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LIBRARY OF THE 
UNIVERSITY OF ILLINOIS 
AT URBANA-CHAMPAIGN 


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TEXTBOOK 


ON 


UO Hel Meee | Rg Ye 


FOR THE USE OF 


SCHOOLS AND COLLEGES. 


BY 


JOHN WILLIAM DRAPER,’ M.D., 


Professor of Chemistry in the University of New York, Member ot the American 
Philosophical Society, &c. 


With nearly Three Hundred Illustrations. 


HARPER & BROTHERS, PUBLISHERS, 


82 CLIFF STREET, NEW YORK. 


1846. 


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Entered, according to Act of Congress, in the year 1846, . 
Vike By Harrver & Brotuers, ) 
In the Clerk’s Office of the Southern District of New York. 

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PREFACE 


Tuts text-book on Chemistry, intended for the use 
of colleges and schools, contains the outline of the 
course of Lectures which I give every year in this 
University. 

I do not, therefore, present to teachers an untried 
work. Its divisions and arrangement are the result 
of an experience of several years; an experience 
which has proved to me that there is required a text- 
book of small size, so that students can pass through 
it readily in the time usually devoted to Chemistry. 

. very instructor in this science must have observ- 
ed that the ordinary “ Treatises” or “ Elements” are 
by no means suited to his wants. When they are 
employed in the class-room, there are large portions 
which have to be omitted, and other portions too 
briefly explained. In fact, to study Chemistry suc- 
cessfully, the first thing which is wanted is a com- 
pendious book, which sets forth in plain language 
the great features of the science, without perplexing 
the beginner with too much detail. 

A 2 


vi PREFACE. 


It will be understood, therefore, that this work, 
with little pretensions to originality, except where 
directly specified, occupies a different field from that 
of the larger treatises. It is intended as a manual, 
arranged in such divisions as practice has shown to 
be suitable for daily instruction. It is the exposition 
of what I have found to be a satisfactory method of 
teaching; and of its success our annual examinations 
are the best testimonial. 

The unsuitableness of large text-books has led to 
many attempts to reduce their size by abstracts and 
compendiums ; but the difficulty can never be avoid- 
ed by that means; the very structure of such works 
is faulty. We never want to use all that an author 
knows or can possibly say on the subject. It has 
been well remarked, that “ The greatest service 
which can be rendered to our science, is for some 
person who has had the management of large classes 
for several years to sit down and write a book, set- 
ting forth what he said and what he did every day in 
his Lectures. That is the thing we want.” 

While, therefore, this book is offered to instructors 
as a practical work, the object of which is to display 
the leading features of the science, I have endeavored 
to make it a representation of the present state of 
Chemistry. In this respect many of our most popu- 
lar works are defective. ®? Among them I should not 
know where to turn for a simple exposition of the 


PREFACE. Vii 


Wave theory of Light or of Ohm’s theory of Voltaic 
Currents ; yet the one is the most striking result of 
physical research, and the other is connected with 
the fundamental facts of Electro-chemistry. 

To the treatises of Hare, Kane, Graham, Gregory, 
Fownes, Dumas, and Millon I must formally state 
my obligations. In Descriptive Chemistry I have fol- 
lowed them closely; and in those cases which are 
much more common than is generally supposed, 
where there are differences in the imputed proper- 
ties of bodies, I have consulted, wherever I could, 
either original memoirs or the annual reports of Ber- 
zelius. 

The number of wood-cuts, representing experi- 
mental arrangements, which have been introduced, 
will give to a beginner a clearer idea of the practical 
part of each Lecture, and, in our country colleges, 
may sometimes supply the place of defective or in- 
complete apparatus. To each Lecture is appended a 
set of questions. ‘They enable a young student more 
quickly to apprehend the doctrines which are before 
him. | 

Joun Witiiam Draper. 


University of New York, 
July 6, 1846. t 


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CONTENTS, 


Lecture ge | Page 
I. Constitution of Matter : A - a 6 3 pues! 


II. Constitution of Matter (continued) . ae eae A a KS 
Ill. Heat . : é ; : i 4! 
IV. Expansion of Gaps a Liquids 2 : ; * 15 
V. Expansion of Liquids and Solids. i , : - 420 
VI. Expansion of Solids . é ; : : A m ote 
VII. Capacity of Bodies for Heat . és : : ° - 28 
VIII. Capacity for Heat and Latent Heat : F - » oe 
IX. Latent Heat (continued) . ; “ . : : «= 36 
X. Vaporization . : : : PF e 4 ~ 440 


XI. Ebullition . : 3 = . € ‘ 7 E . 44 
XII. Vaporization . : : : eK 
XIII. Evaporation and Interstitial Radiation y 3 : Sieaict 
XIV. Conduction : 5 f 3 : ‘ ; Oo 
XV. Radiation . t : ; é oo OS 
XVI. Theory of the Micchancde of Heat : F 5 4 aaGi 

XVII. Nature of Light ; i ‘ a 4 ae 
XVIII. Constitation of the Solar Sdboteniti ‘ . ; 2 ae oe 


XIX. Wave Theory of Light . , , : ‘ : 708 
XX. Wave Theory of Light (continued) . . A 4 w 162 
XXI. Wave Theory of Light (continued) . . : é . 86 


XXII. The Tithonic Rays . : ‘ 4 . : - OO 
XXIII. Theory of Ideal Coloration ; ‘ ; 3 : . 94 
XXIV. Electricity . : : : : : : x 97 

XXY. Theory of Electrical Endackion ; . : = LO1 
XXVI. Laws of the Distribution of Electricity abet General The- 

ories . © r - 105 

XXVII. Faraday’s osear of Bilectrical Polaraatios ; : Ral 550 
XXVIII. Voltaic Electricity . - 4 : - ; - . 115 
XXIX. Effects of Voltaic Electricity . : 3 : : . 120 
XXX. The Electro-chemical Theory . : « 125 


XX XI. Ohm’s Theory of the Voltaic Biles Masten ; ~ 131 
XXXII. Electro-dynamics—Thermo-electricity . : : . 137 
XX XIII. The Chemical Nomenclature . : : : 4 . 144 
XXXIV. The Symbols. : . ; ‘ Oat: : . 147 
XXXV. The Laws of Combination : . - : ° » 151 
XXXVI. Constitution of Bodies—Crystallization . . . .155 
XXXVII. Chemical Affinity . 3 : there's . -  « 164 


Lecture 


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LXXII. 
LX XIII. 
LXXIV. 
LXXV. 
LXXVI. 
LXXVII. 
LXXVIII. 
LXXIX. 
LXXxX. 
LXXXI. 


a 


CONTENTS. 


Pneumatic Chemistry—Oxygen Gas 
Oxygen (continued) 

Hydrogen 

W ater 4 

AE a Ban men iS Bo Ap : 
Atmospheric Air (continued) . 
Atmospheric Air (continued) . 
Compounds of Nitrogen and Oxygen 
Compounds of Nitrogen and Oxygen 
Sulphur 

Compounds of Sulphur sal Oxstin 
Sulphur and Phosphorus 

Compounds of Phosphorus and asda 
Chlorine . 2 : 5 2 
Chlorine (cobvitstdluéd) 

Bromine—F luorine—Carbon . 

Carbonic Acid : 
Granoenn in to Biinon —Aramorient 
General Properties of the Metals .° 
Potassium ; 

Sodium—L ‘chinmB arium 

Strontium Calcite! Magn esi meme bantieeteed 
Manganese—Iron : 
Iron—Nickel—Cobalt—Zinc . 
Cadmium—Tin—Chromium—Titanium 
Arsenic 


Arsenic—Antimony—T itr ice Drastic Oe priee 


Lead—Bismuth—Silver 
Mercury—Gold—Platinum, &c. 

General Properties of Organic Bodies . 
The Non-nitrogenized Bodies ; 
Action of Agents on the Starch Group . 


The Metamorphosis of the Starch Group by Nitrogen 


ized Ferments : 
The Derivatives of Seriteniativs ilenias 
The Derivative Bodies of Alcohol 
Oxydation of Alcohol 
Derivatives of Acetyle—the Keakehddtl Group 
The Wood Spirit Group 
The Potato Oil Group—the Bapilegli Gia 
The Salicyle and Cinnamyle Groups 


The Nitrogenized Principles—Ammonia—Cyanogen 


Bodies allied to Cyanogen . : : 
Mellone—Urea : i : ; 
The Vegetable Acids . ; : . 


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LXXXITq. 
LXXXIV. 

LXXXV. 


LXXXVI. 
LXXXVIL. 


LXXXVIII. 
LXXXIX, 


CONTENTS. Xl 


: Page 
The Vegetable Alkalies : 2 - ; : 367 
The Coloring Principles : ; : : : mar a! 
The Fatty Bodies ; . oto 
The Resins, Balsams, and Ritlon'c arising in despre 
Distillation : ; . 380 
Animal Chemaintey= Deeetaen aa Neeihan, : . 384 
Origin and Deposit of the Fats and Neutral Nitrogen- 
ized Bodies. : : . 387 
The Transmission of Food fnroten the evereas : . 392 
Nature of the Processes of Secretion . «hee oe 


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INTRODUCTION. 


CONSTITUTION AND GENERAL PROPERTIES OF MATTER, 


LECTURE I. 


Constitution or Marrer.—Distinction between Chem- 
istry and Natural Philosophy.—General Division of 
Chemistry.—Active Forces and Ponderable Bodies.— 
Proof of the Atomic Constitution of Matter in the Cases 
of a Solid and a Gas.—Atoms are inconceivably small._— 
They are not in contact— They are unchangeable and 
indestructible. 


THE physical sciences are divided into two classes, com- 
prehended respectively under the titles of Narurat Put- 
LosopHy and CHEMISTRY. 

Natural Philosophy investigates the relations of masses 
to one another. The movements of tides in the sea un- 
der the conjoint influence of the sun and moon; the de- 
scent of falling bodies to the earth; the pressure of the 
atmosphere; the various modes of rendering mechanical 
forces available, by the action of levers, pulleys, wedges, 
screws; the phenomena of the planetary bodies, which 
move in elliptic orbits around a central mass: these are 
all objects fur the consideration of Natural Philosophy. 

Chemistry considers the relations of particles to each 
other; it investigates the properties and qualities of differ- 
ent kinds of matter, their mutual influence, and the ac- 
tion of the imponderable principles upon them. It treats 
of the causes of those invisible movements which the 
molecules of bodies around us unceasingly undergo. It 
also includes many of the phenomena of living beings, 
explains the objects of respiration, digestion, and other 
such animal functions. | 

Every change taking place in bodies is due to the op- 
eration of some active force. It is one of the first princi- 


~ Into what classes are the physical sciences divided? Of what phenom. 
_ ena does natural philosovhy treat? What are the objects of chemistry ? 
A 


2 CONSTITUTION OF MATTER. 


ples in philosophy, that no movement or mutation can oc- 
cur in any thing spontaneously ; we must always refer it 
to a disturbing cause. Under the influence of heat, bodies 
increase in size; under that of electricity, some are dis- 
severed into their component elements; under that of 
light, vegetables form from inorganic materials their or- 
ganized structures. The science of chemistry resolves 
itself; therefore, into two divisions: the first, embracing the 
consideration of the active forces of chemistry; the sec- 
ond, the objects on which those forces operate. 

These active forces are Heat, Light, and Electricity. 
By the older chemists, they are designated as imponder- 
able substances, from the circumstance that they do not 
affect the most sensitive balances. 

We can form no idea of the properties of bodies dis- 
engaged from the influence of these principles. Thus 
we find all material substances existing under one of 
three conditions, solid, or liquid, or gaseous; and the 
majority can assume either of these conditions under the 
influence of heat. Water, for instance, at low tempera- 
tures, exists in the solid state as ice; at higher tempera- 
tures, it assumes the liquid condition ; and, at still higher, 
eebibits the gaseous form. We SBE: therefor) that it is 
the degree of heat to which it is exposed which deter- 
mines its physical state. 

One of the first problems which the chemist has to solve, 
is that of determining the true constitution of matter ; not 
of matter in the abstr. act, but as placed under the infudnee 
of these external powers. 

Fig. 1. All the phenomena of chemistry 
prove that material substances con- 
sist of indivisible and exceedingly mi- 

-nute portions, called Aroms, which 
are placed at certain distances from 
one another, those distances being 
variable and determined by the agen- 
cy of active forces. 

Thus, if we take a copper ball, a, 
Fig. 1, an inch in diameter, and provide a ring, 4, of such a 


What are the two leading divisions of chemistry? What are the act- 
ive forces of chemistry? Why are these called imponderable bodies? 
What are the three forms of substances? What is it that determines 
these forms? What is the constitution of matter? Describe the arrange- 
ment of the instrument, Fig. 1, and its use. 


CONSTITUTION OF MATTER. 3 


size that the ball at common temperatures can readily pass 

through it, and having suspended the ball by means of a 

chain to a stand, d, expose it to the flame of a spirit lamp, 

c, as it becomes warm it will be found to dilate, so that, 

in the course of a few minutes, it can no longer pass read- 

ily through the ring, but if placed thereon, remains sup- 
orted. 

While under these circumstances no visible change has 
taken place in the general properties of the ball; its 
weight remains the same as before, its aspect 1s the same. 
We conclude, therefore, that its volume has increased be- 
cause we have raised its temperature. 

But now, the lamp being removed, the ball still resting 
on its ring, begins to cool. In the course of a few min- 
utes it spontaneously drops through the ring. It has, 
therefore, become less than it was while hot, and, in point 
of fact, when its original temperature is reached, it has re- 
covered its original size. 

From this simple, but beautiful experiment, very im- 
portant conclusions may be drawn. ‘The copper ball, in 
cooling, becomes less: a fact which at once suggests the 
idea that its constituent particles have approached each 
other. In its warm and dilated state, although it exhibit- 
ed no appearance of transparency, or of interstitial spaces, 
or pores through which light might pass, its particles were 
not touching one another, for had they been in actual con- 
tact they could not have more closely approached one an- 
other, and contraction could not have taken place. 

As all bodies contract during the act of cooling, we in- 
fer that the particles of which they are composed are 
separated from each other by intervening Fig. 2. 
speces, and experiments such as that we 
have been considering suggest two im- 
portant observations: Ist. That all mate- 
rial substances are made up of small par- 
ticles which do not touch each other; and, 
2d. That the intervening spaces may be yva- 
ried at the pleasure of the experimenter. 

Let us consider a second illustration 
which will lead us to the same conclusion; selecting, as 


2 
= 
= 


_ Why, in this experiment, does the ball finally drop through the ring? 
Could contraction take place if its particles were already in contact? 
What two conclusions do these facts suggest? 


ac oo 


4 CONSTITUTION OF MATTER. 


the object of our experiment, atmospheric air, a substance 
differing in all its physical and chemical relations from 
the copper ball. Let us take a tube of glass half an inch 
in diameter, and bent in the form exhibited in Jig. 2, a, 
c,d. The faben is closed at its upper end, a; it is yee 
at c, and over its open extremity, at d,a bag ae India rub- 
ber is tied, air tight. In the tube there has been previ- 
ously inclosed a sufficient quantity of water to fill all the 
portion 4, c, d, but the space from a to } is occupied by 
atmospheric air. It is to the volume of this atmospheric 
air that our attention is directed. 

If we compress the India rubber bag in our hand, the 
volume of the air instantly becomes less, the diminution 
being greater in proportion as the pressure is greater. 
Now, i it is inconceivable that this phenomenon should en- 
sue, unless the aerial particles approached each other ; 
but. such an approach would be impossible if they were 
already in contact. Two particles could not occupy the 
same space at the same time. 

We conclude, therefore, that for atmospheric air, a 
gaseous body, as well as for copper, a solid, the same 
law holds good, and that both these forms of matter are 
constructed upon the same type; that they are made up 
of particles set at distances from one another, and that we 
can change those distances at pleasure, by resorting to 
changes of temperature, or to mechanical forces. 

Fig. 3. It is worthy of observation, that by proper 
means these interstitial spaces may be greatly 
increased or diminished, and in very many in- 
stances without any striking apparent change 
occurring in the substance under experiment. 
i) Thus, if we take a globe of glass two or three 
<€ 3°, inches in diameter, a, Fig. 3, with a_neck or 
<a> tube, b, proceeding from it, and fill the globe 
full of water, with the exception of a small bubble of air 
which occupies its upper part, while the open extremity 
of the tube, 4, dips beneath some water contained in a 
glass jar, c, then, covering the whole with an air-pump 
receiver, d, proceed to exhaust, we shall find that the little 


~ Describe the instrument represented in J/g. 2. What is the use of 
this instrament? With an increase of pressure, what happens to the in- 
cluded air? Can two particles occupy the same space at the same time ? 
What, then, is the deduction from this experiment? What is the exper- 
iment given in fig. 3 intended to illustrate ? 


= 


SIZE OF ATOMS. 5 


bubble, a, dilates as the machine is worked, and may be 
rendered a hundred-fold greater than at first. In this ex- 
panded condition, its particles must have greatly reced- 
ed from each other, and yet no remarkable physical change 
is to be observed. There are no dark or vacuous spaces; 
but, in this attenuated condition, it possesses the aspect 
which it had when at the common density. 

With these preliminary facts, we may now direct our 
attention, Ist, to the properties of atoms; and, 2d, to the 
interstitial spaces which part them from each other. 

That the atoms of which bodies are composed are ex- 
ceedingly small, we possess abundant proof. By dissolv- 
ing substances in liquid media, and then greatly diluting 
the solution, we can effect a subdivision to an incredible 
extent. A single drop of a solution of sulphate of indigo 
will communicate a blue color to one thousand cubic inch- 
es of water, so that every drop of that diluted solution _ 
contains a portion of the coloring matter. In the same 
manner, by resorting to proper tests, we can show that a 
grain of copper, or silver, or gold, may be divided into 
many millions of smaller parts, each of which may be 
readily recognized. Nor is it alone by these chemical 

rocesses that such a minute subdivision may be effected : 
By the mechanical process of beating with a hammer, 
gold may be extended into leaves which are less than the 
sopaa7 part of an inch thick, a dimension far less than 
the human eye, unassisted by microscopes, can discover, 
for the smallest spherical object visible to it is about 
soya part of an inch in diameter. By other processes, it 
has been estimated that this metal may be divided to such 
an extent, that a single grain will yield 80 millions of 
millions of visible parts. The world of organization fur- 
nishes us with still more striking proofs. There exist 
animalcules of which it would require many millions to 
make up the bulk of a common grain of sand, yet these 
are furnished with digestive and respiratory organs, with 
circulating juices, and with contrivances as elaborate as 
the mechanism of the highest orders of life. How minute, 
then, must the constituent particles be ! 


To what extent can the constituent atoms be removed? To what ex- 
tent can sulphate of indigo be divided? Can similar results be obtained 
from metalline bodies? What evidence have we on this point from me- 
chanical processes? What argument may be drawn from the construc- 
tion of animalcules ? 

A 2 


6 PROPERTIES OF ATOMS. 


All the results of chemistry prove that the ultimate 
atoms of bodies are unchangeable and imperishable. We 
can not effect their destruction, or impress them with new 
or unusual qualities, any more than we can call them into 
existence. Those familiar instances in which it appears 
that material substances are destroyed or dissipated, when 
properly understood, are only cases of transformation, or 
of the origin of new compounds. An atom once created, 
can by no process be destroyed. When, therefore, coal 
disappears in the act of burning, it is not, in reality, a de- 
struction of the particles of which the coal consists, but these 
particles uniting with one of the constituents of the air, 
give origin to a body of a different form, an invisible and 
elastic substance, from which, however, the carbonaceous 
particles could ‘be reobtained by resorting to proper 
methods. It is, moreover, obvious that the continuance 
and stability of the universe itself depend on the fact that 
by no natural process can material atoms be either cre- 
ated or destroyed. 


LECTURE II. 


Constitution or Mattrer.—Of the Interstices between 
Atoms.— They are not casual, but regulated. — Two 
Forces are required to produce this Result,— Cohesion 
and Heat—Proof that these Forces act through very 
limited Spaces.— Analogy between the Structure of Mat- 
ter and the Structure of the Universe. 


Having, in the preceding lecture, established the atomic 
constitution of matter, let us now direct our attention to 
the intervening interstices. 

The distances that part the atoms of a given mass from 
one another are not casual or determined at random ; 
their magnitude is perfectly regulated. Thus, if we take 
a glass bulb, a, fig. 4, with an open neck, 6, and having 
filled the neck with water to a given mark, c, immerse 
its open extremity in a glass of water, d, it will be found 


Are the atoms of bodies either changeable or perishable? How can 
the apparent destruction of bodies be explained? Are the spaces be- 


tween atoms regulated or at random? What is the experiment, ok 4, 


designed to establish ? 


4 ” 


REGULARITY OF INTERSTITIAL SPACES. 7 


that so long as no extraneous cause in- Fig. 4. 
tervenes the water remains perfectly sta- 
tionary at its original point, ¢; but if, by 
the application of a spirit lamp, e, weraise §& 
the temperature of the air included in 
the bulb, it promptly dilates; a dilatation 2 
which, however, does not proceed with “¢™ 
irregularity, for the volume of the air 
steadily increases as the heat is steadily 
continued. Let the lamp now be remov- 
ed, and as the temperature descends the 
water comes back again to its original point, because the 
air recovers if8 original bulk. 

In the same manner, if we repeat the experiment illus- 
trated in Fvg. 3, we shall see that the bubble of air does 
not expand with irregularity as the pump is worked. It 
does not at one mement suddenly dilate, and then remain 
motionless, but for each movement of the pump it increas- 
es correspondingly; and as soon as the pressure is re- 
stored to the interior of the machine; it shrinks back to 
its original size. But these expansions and contractions 
are the result of movements among the constituent atoms, 
which at one time recede farther apart, and at another 
come closer together. It follows, therefore, from these 
considerations, that the distances which separate the con. 
stituent atoms are not determined by chance or at random, 
but their magnitude is strictly regulated. 

To produce these results two forces are required: Ist, 
a force of attraction, which continually tends to draw the 
atoms closer together; 2d, a force of repulsion, which 
tends to remove them farther apart. The distance at 
which they are placed, at any particular moment, is de- 
termined by the balancing of these forces; if the attractive 
force is made to increase in intensity, the particles ap- 
proach ; if the repulsive, they recede. 

Names have been given to these forces, the attractive 
force being known under the name of cohesion; caloric 
or heat appears to be the principle of repulsion. 

All attractive and repulsive forces diminish as the dis- 
tances through which they act increase. The attractive 


Can the same rae, be proved by resorting to other disturbing pro- 
cesses? How many forces are required to account for these facts ? What 
is their nature? What is the relation between heat and repulsion ? 


8 SIZE OF INTERSTITIAL SPACES, 


force of the earth, the force of gravitation, is of a certain 
intensity on the surface of our planet, but it diminishes as 
the distances become greater. The forces which connect 
together the bodies of the solar system, and, indeed, one 
planetary system with another, act through great intervals 
of space ; thus the attractive force of the sun, operating 
through many millions of miles, retains the earth in her 
orbit. But the attractive and repulsive forces which de- 
termine the position of the constituent atoms of bodies are 
limited to a very minute space. If we take two leaden 
bullets, and having pared a small portion from the surface 
of each, so as to expose a brilliant metallic spot, bring 
them within an inch of one another, they exert no percep- 
tible attraction, and may be drawn apart with the utmost 
facility ; we may diminish the distance between them to 
the tenth, the hundredth, the thousandth part of an inch, 
and still the same observation may be made; we may 
even bring them in apparent contact, and the attractive 
influence of the particles ofthe one upon those of the other 
is still undiscoverable; but, on pressing them together, 
we can finally bring them within the range of each other’s 
influence, and then they cohere together as though they 
were a single mass, and require a considerable effort to 
separate them. 
The apparatus figured in the margin serves to illustrate 
Fig. 5. the same result. Suspend a cir- 
cular piece of plate glass, a, Fig. 
5, an inch in diameter, to one of 
the arms of a balance, 4, c, counter- 
poising it on the opposite arm by 
ga Weights placed in the scale pan, d. 
Beneath the plate of glass place a 
cup, é, containing some quicksilver, 
and it can be proved that so long ds the glass is at a sen- 
sible distance from the surface of the quicksilver, no at- 
traction between them is exhibited, for were such the 
case, the arm of the balance should incline, and the glass 
descend. As long as the smallest perceptible space inter- 
venes, no attractive action is developed; but on bringing 
the two surfaces in contact, they cohere ; and now it re- 


Through what spaces can these forces operate? How can this be proved 
by leaden bullets? Describe the apparatus, Jig. 5. What is its use? 
What the fact which is proved by it? 


CONSTITUTION OF MATTER. 9 


quires the addition of a considerable weight in the scale 
pan to draw them asunder. This result does not depend 
on the pressure of the air, for it equally takes place in a 
vacuum. 

From experiments of this kind, therefore, we gather 
that the spaces through which molecular attractions and 
repulsions can act are very limited, and it follows of ne- 
cessity that the interstices which separate the atoms of 
bodies are exceedingly minute, for through those spaces 
the action of these forces extends. If the limiting distance 
through which molecular attraction and repulsion can 
reach is, as there is reason to believe, from some of the 
experiments of Newton, less than the millionth of an inch, 
we are entitled to conclude that the interstitial spaces are 
much smaller, 

To what, then, do these results finally point in regard 
to the constitution of matter, if, as we have seen, the con- 
stituent atoms themselves are inconceivably minute, and | 
the spaces that separate them as small as we have reason te 
conclude? We may look upon the universe as represent- 
ing on a grand scale the constitution of matter on a minute 
one. The planetary bodies which compose the solar sys- 
tem, and which are held in their orbits by the attraction 
of a central mass, are separated from one another by enor- 
mous spaces, to which their own magnitudes bear but an 
insignificant proportion. About thirty such bodies, great 
and small, compose the group or family to which our 
earth belongs. But as there are systems of opaque plan- 
etary bodies, so also there are systems of self-luminous 
suns, which compose together colonies of stars. In the 
universe myriads of such systems exist, separated from 
one another by spaces so great that the mind can form no 
just idea of them. A planet, such as Jupiter with its at- 
tendant satellites; a self-luminous star, like our sun with 
its surrounding bodies; a group of shining stars, such as 
are scattered over our skies; a collection of such groups 
as form the nebular masses; these, in succession, furnish 
us with a series of illustrations on a scale continually in- 
creasing in dimensions of the constitution of matter, which 
is made up of isolated atoms placed at variable distances 

Does the experiment depend on the pressure of the air? What are 


the limiting distances through which molecular forces can act? State the 


analogy between the constitution of the universe and the constitution of 
matter ? 


10 CONSTITUTION OF MATTER. 


from each other, the size of these atoms bearing an insig- 
nificant proportion to the spaces intervening between them. 

The human mind is so constituted that it is unable to 
appreciate whatever is exceedingly great or exceedingly 
small. We can neither attach a precise idea to the mag- 
nitudes and grander relations of the universe, nor to the 
atomic constitution of a grain of dust. Hereafter, when 
we come to speak of the phenomena of light, we shall see 
that by following the same philosophical methods which 
have been cultivated with such success in astronomy, and 
which have furnished us with a general view of the con- 
stitution of the universe, we also can obtain a general view 
of the scale which has been used in the constitution of 
material bodies, a scale which brings before us new ideas 
of time and space. When we are told that in the mill- 
ionth part of a second a wave of violet light pulsates or 
trembles seven hundred and twenty-seven millions of 
times, and that, if we divide a single inch into ten millions 
of equal parts, this violet wave is only one hundred and 
sixty-seven of such parts in length, we obtain a glimpse 
of the scale on which material bodies are composed, and 
must confess the inability of the human imagination to 
form a proper conception of such results, though we may 
feel a just pride in the intellectual power which has ascer- 
tained them. 


PAR IOI 


THE FORCES OF CHEMISTRY. 


LECTURE III. 
Heat.—Preliminary Ideas of the Nature of Heat.—In- 


Jluence of Heat in the inorganic and organic Worlds — 
Modes of Transference—LIllustrations of Expansion.— 
feat determines the Magnitude and Form of Bodies— 
Affects our Measures of Time and Space—Determines 
the Distribution of Animals and Plants. 


Writers on chemistry signify by the term Caloric, the 
agent which excites in our bodies the sensation of heat. 
By some, however, heat and caloric are used synonymous- | 
ly. Those who look upon this force as if it were a ma- 
terial and imponderable substance, ascribe to the particles 
of caloric a self-repulsive power, and an attraction for 
the particles of ponderable bodies. 

So great is the control which caloric exercises over all 
kinds of chemical changes, that few experiments can be 
made in which transformations of substances take place 
without contemporaneous disturbances of temperature. 
In some, heat is evolved ; in others, cold is produced. To 
this agent, moreover, we so constantly resort for the pro- 
motion of molecular changes, that the chemist has been 
not inaptly designated the Philosopher by Fire. 

It is not alone in the inorganic world that the influences 
of caloric are traced. Life can» not take place except 
within certain limits of temperature; limits which.are 
comprehended between the freezing and the boiling points 
of water, that is, within one hundred and eighty degrees 
of our thermometer; and, in point of fact, within a nar- 
rower range than that. It is, therefore, not alone in 
chemistry, but also in physiology, that the relations of 
this agent are of interest. 

What is caloric? What is heat? On the hypothesis that caloric is 
an imponderable substance, what are its properties? Why is it that the 


study of caloric is of such great importance in chemistry? Within what 
limits of temperature can living things exist ?, 


12 HEAT PRODUCES EXPANSION. 


When an ignited mass, as a red-hot ball, is placed in 
the middle of a room, common observation satisfies us 
that it rapidly loses its heat; its temperature descending 
until it becomes the same as that of surrounding walls 
and other bodies. This loss is due to several causes. A 
part of the heat is carried away by contact with the body 
which supports the ball, a part by certain motions estab- 
lished in the surrounding air, and a part by radiation. 
This removal passes under the name of transference, and 
as soon as the temperature has declined to that of the ad- 
jacent bodies, an equilibrium is said to have been attained. 

There are two methods by which caloric can be trans- 
ferred: Ist. By radiation; 2d. By convection. Of the 
former we have two varieties—general radiation, and in- 
terstitial radiation. 

Fig.6. | Under the influence of an increasing tempera- 
“| ture substances expand. This takes place, what- 
ever their form may be, whether solid, liquid, or 
gaseous. The experiment which is illustrated by 
Fig. 1, establishes this fact in the case of a copper 
ball; and that the same law holds good for liquids, 
{ )° may be proved by taking a glass tube, a, 6, Fig. 
6, open at the extremity, a, but having a bulb, c, 


blown upon it at the other end. The bulb and a 
part of the tube, as high as 3, is to be filled with 
any liquid substance, such as water, spirits of wine, or 
Fig.7, Oil; and the heat of a lamp, d, applied. As the 

~ liquid becomes warm, it dilates, as is shown by its 
) rising in the tube; the dilatation increasing with 
the temperature. 

If now the liquid be removed from the bulb, and 
the tube be inverted, as shown in F%g. 7, in a glass 
of water, we can prove the same fact for gaseous 
A substances, taking, as the type or representative of 
ey them, atmospheric air; for, on simply grasping 
“> the bulb, c, in the hand, the air which is in it di- 
lates with the warmth, and bubbles pass in succession 
from the open end of the tube, through the water in the 
glass, d. 


Through what causes does the temperature of a body descend? What 
is meant by transference and by equilibrium? In how many ways can 
caloric be transferred? How many varieties of radiation are there? By 
what means can it be proved that solids, liquids, and gases expand as 
their temperature rises, and contract as it descends? 


EFFECTS OF HEAT. 13 


We conclude, therefore, that solids, liquids, and gases 
expand as their temperature rises, and contract as their 
temperature falls. 

The magnitude of all objects around us is determined 
by their temperatures. A measure which is a yard long 
in summer is less than a yard in winter; a vessel which 
holds a gallon in winter will hold more than a gallon in 
summer. And as the degrees of heat vary not alone at 
different seasons of the year, but also during every hour 
of the day, it is clear that the dimensions of all objects 
must be undergoing continual changes. The appearance 
of stationary magnitudes which such objects present is 
therefore altogether a deception. 

Heat thus determines the size of bodies; it also de- 
termines their form. As we have said, there are three 
forms of bodies, solid, liquid, and gaseous. A mass of 
ice, if exposed to a temperature of above 32°, melts into 
water; and if that water be raised to 212°, it passes into . 
the form of steam—a gaseous body. The assumption of 
the solid, the liquid, or the gaseous condition, depends 
on the existing temperature. 

In the same manner that it affects our measures of 
space, caloric affects our measures of time. Cloéks and 
watches measure time by the vibrations of pendulums, or 
the oscillations of balance wheels, the uniformity of the 
action of which depends on the uniformity of their size. 
When the temperature rises, the rod of a pendulum 
lengthens, and its vibrations are made more slowly; the 
clock to which it is attached loses time. When the 
temperature declines, the pendulum shortens; it beats too 
quick, and the clock gains. Similar observations may be 
made in the case of watches. ‘To obviate these difficulties 
many contrivances have been invented, such as the grid- 
iron pendulum, the compensation balance wheel, &Xc. 
Advantage has also been taken of such substances as ex- 
pand but little for a given elevation of temperature; and 
thus excellent clocks have been made, the pendulum rods 
of which were formed of a slip of marble. 

The natural, as well as the artificial measures of time, 
depend on the influence of heat. Our unit of time—the 


Is there any variation at different seasons in the length of measures or 
the capacity of vessels? What is it that determines the form of bodies ?’ 
How can caloric affect our measures of time? By what contrivances has 
this difficulty been avoided ? : 


14 CONNECTION OF TEMPERATURE AND TIME. 


day —is the period which elapses during one complete 
rotation of the earth on her axis. The length of this pe- 
riod is determined by the mean temperature of her mass. 
Should the mean temperature of the whole earth fall, her 
magnitude must become less, or, what is the same thing, 
her diameter must shorten. It results from very simple 
mechanical principles, that a given mass, the dimensions 
of which are variable, rotating on its axis, will complete 
each rotation in a shorter space of time as its diameter be- 
comes smaller. Thus, when we tie a weight to the end 
of a thread, and, swinging it round in the air, permit the 
thread to wrap round one of the fingers, as the thread 
shortens by wrapping, the weight accomplishes its revolu- 
tion in a less period. Now, transferring this illustration 
to the case before us, if the mean temperature of the earth 
had ever declined, she must have become less in size, and, 
therefore, turned round quicker, and the length of the day 
must have necessarily been less. But astronomical ob- 
servations, for a period of more than 2000 years back, 
prove conclusively that the length ys the day has not 
changed by so small a quantity as the ;1, part of a second, 
and we therefore are warranted in inferring that the mean 
temperature of the globe has not perceptibly fallen. 

The distribution of heat on the surface of the earth de- 
termines, for the most part, the distribution of animals 
and plants; to each climate its proper denizens are as- 
signed. Itis this which confines the lion to the torrid re- 
gions, and the white bear to the frigid zone. In the case 
of man, who has the power of accommodating his diet and 
his dress to external requirements, almost any part of the 
earth is habitable. Plants, like the inferior animals, have 
their localities determined chiefly by the influence of heat. 
It is for this reason that even in tropical climates, if we 
ascend from the foot to the top of a very high mountain, 
we successively pass through zones occupied by trees 
and plants which, differing strikingly from one another, 
have analogies with those which occupy respectively the 
torrid, the temperate, and the frigid zones, on the general 
surface of the earth. 


Do these disturbances affect the natural as well as the artificial meas- 
ures of time? How ean it be proved that the mean temperature of the 
earth has not for many centuries changed? What is it that chiefly de- 
termines the distribution of plants and animals? 


EXPANSION OF GASES. 15 


LECTURE IV. 


ExpaNsiIon or Gases AND Liquips.—Rudberg’s Law.— 
Regularity of Gaseous Expansion.—Ascentional Power 
of expanded Gias.—Amount of Air contained in the same 
Volume at different Temperatures—Gas Thermometers. 
—LExpansion of Liquids— The Mercury Thermometer. 


Ir we compare together the three forms of bodies, as 
respects their changes of volume under the influence of 
heat, we shall find that for a given rise of temperature, 
gases expand the most, liquids intermediately, and solids 
least of all. To this rule but few exceptions are known ; 
liquid carbonic acid, however, expands about four times 
as much as any gaseous body. 

Recent experiments have proved that gases differ‘'among 
themselves in expansibility, though the differences are 
not to any great extent. Jor the permanently elastic 
gases, atmospheric air may be taken as the type; the ex- 
periments of Rudberg show that it expands ;4, of its 
volume at 32° for every degree of Fahrenheit’s ther- 
mometer. As the same quantity of gas occupies very 
different volumes at different temperatures, it is necessary, 
in this and other such cases, to state some specific tem- 
perature at which the estimate of its volume is made; 
the same gaseous mass occupies a much greater space at 
75° than it does at 32°. In the instance before us, we 
consider the pupinel volume to be that which the gas 
would have at 32°, and as has been said, Srery degree 
above that point will increase the volume by giz of the 
bulk it then possessed. 

Gases expand with uniformity as their temperature in- 
creases. ‘Ten degrees of heat produce the same relative 
effect, whether applied at a low or at a high temperature; 
this regularity probably arises from the want of cohesion 
which the gaseous particles exhibit; as we shall presently 
see, it is not observed in the case of liquids and solids. 


Of solids, liquids, and gases, which expand most by heat? In what 
respect is liquid carbonic acid peculiar? Is there any difference among 
gases in their rates of expansion? What is Rudberg’s estimate of the 
amount of expansion of air? Why are we required in these cases to 
adopt a specific temperature? Do gases expand uniformly. 


16 EXPANSION OF GASES. 


The change in specific gravity of atmospheric air, when 
Fig. 8. it is warmed, is the cause of the rise of 
Montgolfier balloons. These, which 
were invented in France in the year 
1782, consist of a bag, or globe, of light 
materials, such as paper or silk, with an 
aperture at the lower part, through 
which, by the aid of combustible ma- 
terial, as straw or shavings, the air in 
the interior may be rarefied. On a 
small scale, they may be made of thin 
tissue paper, pasted together so as to 
form a sphere of two or three feet in diameter, an aperture 
being cut in the lower portion six inches or morein width, 
and beneath it a piece of sponge, soaked in spirits of wine, 
suspended. This being set on fire, the flame rarefies the 
air in the interior of the balloon, which, though it might 
be at first flaccid, soon dilates, and the whole apparatus 
will now rise in the air, precisely on the same principle 
that a cork rises from the bottom of a vessel of water. 

From the circumstance that the volume of air changes 
so readily with changes of temperature, contracting eae 
the influence of cold, and dilating under that of heat, it is 
plain that in different climates on the earth’s surface a 
very different amount of atmospheric air is included under 
the same measure. A vessel which will hold precisely 
one ounce weight at the mean temperature of New York, 
will hold more than an ounce in the cold polar regions, 
and less than an ounce in the tropics. In the former sit- 
uation the air is more dense, because it is ina contracted 
condition by reason of the low temperature, and therefore 
a greater weight is included under a given volume; in 
the latter, the reverse is the case. These facts are sup- 
posed to be connected with certain physiological results, 
as we shall hereafter see. 

The expansions of atmospheric air taking place with 
regularity as the temperature rises, that substance is oc- 
casionally employed as a means of thermometric admeas- 
urement. The air thermometer, called also Sanctorio’s 
thermometer, but which was invented by Galileo about 


What are Montgolfier balloons, and why do they rise? Why is it that 
the weight of air in a given measure is different at different places? De- ~ 
scribe the thermometer of Sanctorio. By whom was it really invented ? 


GAS THERMOMETERS. 1? 


1603, consists of a tube of glass, a, Fig. 9, ter- Fis. % 
minated at its upper extremity by a bulb, 4; the 
other end of the tube being open, dips beneath 
the surface of some colored water in a cup or res- 
ervoir, c, which serves also as a foot or support to 
the instrument. The bulb and part of the tube 
are full of air, the remainder of the tube is occupi- 
ed by the colored water, which by its movements 
up and down serves to indicate changes in the 
volume of the included air. To the side of the 
tube a scale of divisions is afixed, and the tube is 
not arranged so tightly in the neck of the reservoir but 
that there is a free passage for the air in and out of that 
part of the instrument. On touching the ball with the 
fingers, the air within it becomes warm, dilates, and de- 
presses the liquid in the tube, or, on touching it with any 
cold body, it contracts, and the liquid rises. 
This form of thermometer is liable to a dif- 
ficulty which renders it impossible to rely 
upon its indications, except under particular 
circumstances. It is affected by variations of 
atmospheric pressure, as well as by changes 
of heat. To prove that this is the case, place 
such a thermometer under the receiver of an 
air pump, as shown in Frg. 10; on producing 
the slightest degree of rarefaction, the liquid 
in the tube is instantly depressed, and on re- 
storing the pressure of the air, it returns to its original 
position. 
The differential thermometer , Fig. 11. a 
is a gas thermometer, so arrang- 
_ed as to be free from the fore- 
going difficulty. It consists of a 
glass tube, a 6, Frg. 11, bent into 
the form represented in the fig- 
ure, with a bulb blown on each 
extremity. To the horizontal 
part a scale of divisions is afixed. The bulbs are full-of 
atmospheric air, and in the tube there is a small column 
of colored liquid, which serves by its movements as an in- 


' How can the use of this instrument be illustrated? By what disturb- 
ing cause is Sanctorio’s thermometer affected? How may that be proved? 
Describe the differential thermometer. 


B2 


18 EXPANSION OF LIQUIDS. 


dex. To understand the action of this instrument, it is 
only necessary to consider what will take place when it is 
carried into a room the temperature of which is very high 
or very low. If the former, the air in both bulbs, becom- 
ing equally warm, will expand in both equally, and the 
Polini of fluid shiek acts as an index being pressed 
equally in opposite directions, does not move at all. If 
the latter, the air in both “hein cooling equally, ¢ contracts 
equally, an again no movement ensues. It is immateri- 
al, therefore, whether we warm or cool both bulbs, the 
shetument is motionless. But if one of the bulbs, c, is 
made warmer than the other, d, movement at once ensues 
in the liquid column from c toward d. Movement of the 
index, therefore, takes place when the bulbs are at differ- 
ent temperatures, and hence the instrument is called a 
differential thermometer. It was formerly of considera- 
ble use in researches connected with radiant heat. 

Fig, 12. Different liquids expand different- 
ly for the same thermometric dis- 
turbance. ‘This is easily shown by 
an apparatus, as £vg. 12, in which 
we have three tubes, a, 6, c, with 
bulbs on their ends, dipping into 
a trough, f, of tin plate. The tubes 
F {| and bulbs should be all of the same 

© size, and filled with the liquids to be 
tried to the-same height. To each a scale is annexed. 
Let a be filled with quicksilver, 6 with water, and ¢ with 
alcohol; on pouring hot water into the trough, two phe- 
nomena are witnessed: Ist. All the liquids expand; 2d. 
They expand unequally when compared together, the 
mercury expanding least, the water intermediately, and , 
the alcohol most. 

Unlike gases, all-liquids expand irregularly as their 
temperature rises, a given amount of heat producing a 
much greater effect at a high than at a low temperature. 
Ten degrees of heat, applied to a given liquid at 200°, 
will produce a greater expansion than if applied at 100°. 
The reason appears to be, that as a liquid dilates its co- 


If this instrument be carried into a warm and then into a cold room, 
does its index move? Why is it called differential thermometer? How 
can it be shown that different liquids expand differently? Of mercury, 
water, and alcohol, what is the order of expansion? Do liquids, like gas- 
es, expand with regularity? What is the cause of the difference? 


\ 


THE MERCURIAL THERMOMETER. 19 


hesive force becomes less, because its particles are being 
removed farther from each other; and, as the cohesive 
force weakens, its antagonistic power, the heat, produces 
a greater effect. 

Advantage is taken of the properties of liquids 7"8- 13- 
in the making of thermometers. Tor these pur- 
poses, alcohol and mercury are the fluids selected. 
The mercurial thermometer consists of a fine cap- 
illary tube, vg. 13, with a bulb blown on one 
end; the bulb and part of the tube are to be fill- 
ed with quicksilver, and the air expelled from the 
rest of the tube by warming the bulb until the 
metal rises by expansion to the top of the tube, 
and at that moment hermetically sealing the glass 
by melting the end of it with a blow-pipe. As 
the thermometer cools, the quicksilver retreats 
from the top of the tube, and leaves a vacuum 
above it. 

It remains now to annex such a scale to the [4 
instrument as may make its indications compar- 
able with other instruments. ‘To effect this, 
the thermometer is plunged into a vessel con- 
taining melting ice or snow, and opposite the 
point at which the quicksilver stands is marked 
32°, It is then transferred to another vessel in 
which water is rapidly boiling, and the point op- 
posite which it then stands is marked 212°. The inter- 
vening space is divided into 180 equal parts; these are 
degrees, and similar divisions are made on the scale for 
all points above 212°, and below 32°. The zero point, 
or cipher of the scale, is therefore 32 degrees below the 
freezing point of water. 

The melting of ice and the boiling of water are the fix- 
ed thermometric points. They have been selected for the 
purpose of rendering thermometers comparable with each 
other. The numbers which are attached to these points 
are arbitrary, and accordingly three different scales have 
been introduced in different countries. That which is 
commonly used in America and England is the Fahren- 


For making thermometers, what liquids are selected ? How is the mer- 
curial thermometer made? Is there a vacuum above the mercury in the 
tube? How is the scale adjusted? What is the freezing and what the 
boiling point? What is meant by the zero? What are the fixed points? 
Why are these fixed points employed? What three scales have been 


~ introduced ? 


20 THE MERCURIAL THERMOMETER. 


heit scale, which, as we have just seen, makes the melting 
point of ice 32°, and the boiling of water 212°. In 
France, the Centigrade scale is employed; this has for 
the melting of ice 0°, and for the boiling of water 100°. 
In some parts of Europe, Reaumur’s scale is used, the 
points of which are respectively 0° and 80°. Chemical 
authors always specify the thermometer they use by a 
letter attached to the numbers; thus, 212 F, 100 C, 80R, 
refer to the boiling of water on Fahrenheit’s, the Centi- 
grade, and Reaumur’s scales. It is obvious that these de- 
grees are readily convertible into each other by a simple 
arithmetical process. 


LECTURE V. 


Expansion or Liquips anp Sotips.—Importance of the 
Thermometer.—Alcohol Thermometer.—Point of Max- 
emum Density of Liquids—Maximum Density of Wa- 
ter connected with Duration of the Seasons —Expansion 


of Solids. 


From the considerations advanced in Lecture III., we 
can perceive the importance of the thermometer. As all 
our measures of space and time are affected by variations 
of temperature, the thermometer, which measures those 
variations, must necessarily be one of the fundamental 
instruments of physical science. If we state that a given 
. object is a foot long, we must specify the temperature at 
which the measure was taken, for at a lower temperature 
it will be less than a foot, and at a higher it will be more. 

There are several peculiarities which quicksilver pos- 
sesses that eminently fit it to be a thermometric fluid. 
1st. It can always be obtained in a state of uniform purity. 
2d. It expands with greater regularity than most liquids, 
as its temperature rises, and when included in a bulb of 
glass, as in the common instrument, the irregularity of 
expansion of the glass almost exactly compensates the ir- 
regular expansion of the quicksilver, and hence the true 


What is the Centigrade scale? What is Reaumur’s? Can these be 
converted into each other? Why is the thermometer such an important 
instrument ? What are the qualities which quicksilver possesses which 
fit 1t for these uses ? 


MAXIMUM DENSITY OF WATER. 21 


temperature is very accurately marked. 3d. The range 
of temperature between the points of solidification and 
boiling is great, the former being —39° Fahrenheit, and 
the latter at 662° Fahrenheit; that is, about seven hundred 
degrees. 4th. It does not soil or moisten the tube in 
which it is contained, nor does it adhere thereto, but 
moves up and down with facility. 5th. It is affected much 
more readily than water or spirits of wine by a given 
amount of heat, as we shall see when we come to speak 
uf the capacity of bodies for caloric. 

When very low temperatures have to be measured, 
such as approach or are below the freezing point of quick- 
silver, we resort to thermometers filled with alcohol, tinged 
with some coloring matter to make its movements vis- 
ible. This fluid requires a diminution of temperature of 
more than 180° below the zero of our scale before it 

solidifies, and hence is adapted to the measurement of 
low temperatures. 


If we take some water at 100° Fahrenheit, and, placing zi 


it in a vessel in which we can observe its volumes reduce 
its temperature, we shall find, agreeably to the general 
law heretofore given, that as it cools it contracts. As it 
successively passes through 80, 60, 50 degrees, it exhibits 
a continuous diminution; but as soon as it has fallen be- 
low 39°, although it may still be cooling, it begins to ex- 
pand, and continues to do so until it reaches 32°, when 
it freezes. If we take some water at 32° and warm it, 
instead of expanding, it contracts, until it reaches 39°; 
but from that point, any farther elevation of temperature 
causes it to obey the general law, and it expands. 

It is obvious, therefore, that if we take water at 39°, 
it is immaterial whether we warm it or cool it, it will ex- 
pand. At that temperature, therefore, this liquid occu- 
pies the smallest bulk, and is at its greatest density, for 
neither by cooling nor warming can we reduce it to small- 
er dimensions. The particular thermometric point at 
which this takes place is designated “the point of maxi- 
mum density of water,’ and very exact experiments show 
that it is about 394° Fahrenheit. 

Under what circumstances are alcohol thermometers used? Does water 
contract regularly when cooled from 100° to 32°? Does it regularly ex- 
paud when warmed from 32°? At what thermometric point does that 


change take place? What is the designation given to that point? Why 
is that designation appropriate ? 


7234 POINTS OF MAXIMUM DENSITY. 


There are many liquids which thus have points of max- 
imum density, and which expand previous to assuming 
the solid form. In the act of solidifying, water undergoes 
avery great dilatation, amounting to about 4th of its vol- 
ume ; this is the reason that ice floats upon it. Several 
melted metals exhibit the same phenomenon, and advan- 
tage is taken of the fact in the arts. The alloy of which 
printers’ types are formed, or stereotype plates cast, in the 
act of solidifying, expands, and hence forces itself into 
every part of a mould in which it may be poured, and 
copies it perfectly ; ; the Same is the case with melted cast 
iron. But it is impossible to obtain good castings with 
such a metal as lead, which contracts as it cools, and there- 
fore tends to separate from the surface of the mould, or 
to leave vacant spaces in it. 

The fact that water possesses a point of maximum den- 
sity is connected, to a great extent, with several remark- 
able natural phenomena ; the freezing of water on its 
surface is one of these results. If the water contracted 
as it cooled, the colder portions would descend, and rivers 
or ponds would commence to freeze at the bottom first, 
the solidification advancing steadily upward. Such col- 
lections of this liquid would, during the course of a win- 
ter, become solid masses of ice, and they would greatly 
prolong that season of the year, from the length of time 
required to thaw them. But with things as they at pres- 
ent exist, the coldest water is the lightest; it floats on the 
warm water below; solidification takes place on the sur- 
face, and a veil or screen is soon formed which protects the 
liquid beneath. When the warm weather of spring comes 
on, the ice on the surface is in the most favorable posi- 
tion for melting, and thus the point of maximum density 
of water comes to be connected with the duration of the 
seasons. 

Fig. 14. We have already proved by the 

g instrument represented in Ig. 4, 
pee that solid substances dilate as their 
o temperature rises. The same results 
may be made very apparent by the apparatus, Ig. 14. 


Are there other liquids which have points of maximum density? What 
advantage is taken of this fact in the arts? Why does water freeze first 
on its surface ? How is it that these facts are connected with the dura- 
tion of the seasons ? 


€. 


EXPANSION OF SOLIDS. 23 


Upon a strong basis or wooden board, a 4, let there be 
fastened two brass uprights, ¢ d, with notches cut in them, 
so as to receive the ends of the metallic bar, e. This bar 
should be very slightly shorter than the distance between 
the two uprights, that when it is placed resting in their 
grooves, if we take hold of it and move it, it will make a 
rattling sound as we push it backward and forward. If 
now we pour hot water upon the bar, it dilates, as is 
proved on restoring it to its position between the uprights ; 
it will no longer rattle, for it occupies the whole distance 
between them, and perhaps there may even be a difficulty 
in forcing it into the grooves. 

For the determination of very small spaces, the sense 
of hearing may often be far more effectually employed 
than the sense of sight. 

The pyrometer, eeit: 
of which we have 
several varieties, is 
represented in Fig. 
15. It may serve to 
illustrate the fact g& 
that solid substan- @&s 
ces expand by heat. 
It consists essen- 
tially of a metallic 
bar, @ a, resting at 


one end against an RVR naises on 
immovable prop, e, the other end bearing upon a lever, d. 
The extremity of this lever presses upon a second lever, 
c, which also serves as an index. Upon the index-lever 
a spring acts so as to oppose the lever 4, and the point of 
the index ranges over a graduated scale. 

If now lamps be applied to the bar, it expands, and the 
pressure taking effect on the lever, puts it in motion, the 
index traversing over the scale. On removing the lamp 
the bar contracts, and the spring pressing the lever in the 
opposite direction as soon as the bar is cold, brings the 
index back to its original point. 


How does the instrument, Fig. 14, prove that a metallic bar expands 
when heated? Describe the pyrometer and the mode of using it. 


24 CONTRACTION AND DILATATION OF SOLIDS. 


LECTURE VI. 


EXPANSION oF Soxips.—Contraction of Solids —They 
expand wrregularly.— Different Solids expand different- 
ly.— Points of Maximum Density.— Metallic Thermom- 
eters.— Nature of Thermometric Indications. 


Ir is a popular error, that when solid bodies have been 
heated, they do not return, on cooling, to their original size. 
Without resorting to any experimental proof, a few sim- 

le considerations will satisfy us on this point. If a bar 
of metal be exposed for a length of time in the open air, 
it will of course be subjected to continual changes of tem- 
perature; whenever the sun shines on it it will expand, 
and during the cold night it will contract. If now, on 
cooling, it did not rigorously come back to its original 
size, but remained a little elongated, we should observe it 
increasing from day to day, and no matter how minute the 
difference might be, in the course of time it would become 
perceptible. Public edifices in cities are often surround- 
ed by railings of cast iron, which are constantly exposed 
for years to variations of heat and cold, but did any person 
ever observe them to grow or increase in size? We 
conclude, therefore, that solid bodies, on cooling to their _ 
original temperature, regain their original bulk. 

By linear dilatation we mean increase in one dimension, 
as in length; by cubic dilatation, increase in all dimensions, 
length, breadth, and thickness. Knowing the amount of 
linear dilatation of a given solid, we can easily ascertain 
its cubic dilatation, by multiplying the former by 3. This 
result is near enough for practical purposes. 

Solids expand increasingly as their temperature rises, 
a phenonemon already observed in the case of liquids, 
and due to the same cause—a diminution of the cohesive 
force of the particles, because of their increased distance. 

Compared with one another, different solid substances 


What decisive proof can be given that solids, on cooling to their original 
temperature, come back to their original size? What is linear dilatation ? 
What is cubic dilatation? How can the former be converted into the 
latter? Does the same solid expand uniformly or increasingly as its tem- 
perature rises ? 


COMPENSATION BARS. 95 


expand differently for the same disturbance of tempera- 
ture. This may be shown by having bars of different 
metals, but of precisely the same lengths, adjusted to the 
grooves of the instrument, Fig. 14. Ifa bar of brass and 
one of iron be compared, it wl be found that the brass 
expands more than the iron, for it will entirely fill the dis- 
tance between the uprights, while the iron rattles between 
them. 

This difference of expansion is also shown when two 
long slips of metal are soldered together face to face. If 
we fasten in this manner a slip of brass to Fig. 16. 

a similar slip of iron, as in Fug. 16, in « apd 
which, @ a is the slip of iron and 6d the “\Q | 
slip of brass, at common temperatures the 
compound bar is adjusted so as to be 
straight, but if hot water be poured upon 
it, it immediately curves, as represented 
at ac, the strip of brass being on the out- 
side of the curve; if, on the other hand, it 
be artificially cooled, the curvature is in 
the other direction, as at b d, the iron being on the out- 
side of the curve. All this is obviously due to the fact 
that, for the same disturbance of temperature, the brass 
contracts and dilates much more than the iron. When 
the temperature is raised, the brass becomes the longer, 
d compels the compound bar to curve, it occupying the 
greater length of the curve. When the temperature falls, 
¢° brass becomes the shorter, and the bar curves in the 
)pposite direction. 
By taking advantage of these metallic combinations, 
pendulums and balance-wheels for the accurate measure- 
ment of time have been constructed. The gridiron pen- 
dulum and the compensation balance are examples. 

There are some metallic bodies which exhibit points of 
maximum density in the solid state. Rose’s fusible metal 
is an example. When heated from 32° to 1119, it ex- 
pands, but after that point it contracts, and continues to do 
so until it reaches 156°, at which temperature it is actu- 
ally less than it 3 at 32°, I"rom this point it again ex- 


Do different solids expand alike? Of brass and iron, which expands 
most? Describe the construction of a compound bar, and the effect of 
warming and cooling it. What imstruments are constructed on this prop- 
erty? What are the properties exhibited by Rose’s fusible metal ? 


C 


96 METALLIC THERMOMETERS. 


pands, and continues to do so until it melts, which takes 
place at about 201° Fahrenheit. 

Liquid thermometers have a limited range of indica- 
tion. They can not be exposed to degrees of heat ap- 
proaching the point of solidification, for “then their move- 
ments become irregular; neither can they be used for 
degrees near their boiling point, for if vapor should form, 
the instrument would be destroyed. But as there are 
many metals which require a very great degree of heat 
to melt them, it might be expected that we should find 
among this class bodies well suited for thermometric pur- 
poses. The instrument given in F%g. 15 serves to illus- 
trate such an apparatus, and also the difficulties eucoun- 
tered in its use. From the small extent to which metals 
expand, this form of instrument requires levers, or wheels, 
or some multiplying. machinery connected with it, to make 
the changes more perceptible; but such mechanical con- 
trivances can not be employed without the introduction 


of certain causes of disturbance. Friction occurs on the 


centers of motion, the teeth of the wheels play on each 
other, and therefore the index, instead of moving with 
recularity and precision as the expanding bar presi. 
moves by starts often of several degrees at a time, then 1 
pauses, and once more starts again, the whole moveme t 
being incompatible with exactness. Wik: 
A compound strip of metal, as represented in Fig. 16, 
is free from many of these difficulties, and if of sateen 
Fig. 11. length, it will indicate temperatures” 
with great delicacy. A modifica- 
tion of this instrument is known un- 
der the name of Breguet’s ther- 
mometer. It consists of a very slen- 
der strip of platinum, soldered to a 
similar piece of silver, and curved 
into a helix, or spiral, a 6, Fig. 17. 
It is fastened at its upper extremity 
to a metallic support, cc, and from 
its lower portion an index projects, ° 
which plays over a graduated circle. ‘The expansion of 
silver is more than twice as great as that of platina; 


Why can not liquid thermometers be used for very low and very high 
temperatures? What difficulties occur in the use of this instrument? 
Describe Breguet’s thermometer. 


INDICATIONS OF THE THERMOMETER. 27 


when, therefore, the temperature of the thin spiral rises, 
curvature, with a corresponding motion of the index, takes 
place; and if the temperature falls, there is a movement 
in the opposite direction, as has been already explained. 
This Breguet’s thermometer is one of the most delicate 
instruments we have, for the mass of the spiral is so small 
compared with the mass of mercury in an ordinary ther- 
mometer, that every change in the surrounding tempera- 
ture is followed with rapidity and precision. 

For many purposes in science and the arts, it is necessa- 
ry to determine temperatures above a red heat. Daniell’s 
pyrometer is intended to meet these occasions. It con- 
sists of an arrangement by which the expansion of a bar 
of iron or platinum, while exposed to the heat to be meas- 
ured, is registered. ‘The amount so registered is subse- 
quently determined upon a divided scale, and the tem- 
perature estimated therefrom. By the aid of such an 
instrument very high temperatures may be determined, 
and thus it has been shown that brass melts at 1869° 
Fahrenheit, copper at 1996°, gold at 2200°, and cast iron 
at 2786°. 

The thermometer is commonly regarded as a measurer 
fheat. A little consideration will satisfy us that it is 
ly so in a limited sense; it does not indicate the quan- 
heat present in the bodies to, which it is exposed, 


pm the same well, it stande et ‘the same point ; 
‘se there are very different quantities of caloric 
n the | ‘ases. It is not, therefore, the quantity of heat, 
But the intensity, which it measures; that is to say, not the 
quantity abstractly, but the-quantity contained in a given 
space; and in the mercury thermometer, that space is 
measured by the volume of the mercury in the instrument 
itself. It does not tell how much heat is absolutely present 
in the substances to which it is exposed; and though it 
may stand at the same height in the same quantity of two 
different liquids, it does not follow that those liquids con- 
tain the same amount of caloric, as we are immediately 
to see. 


Why is this instrument so sensitive? Describe the principle of Daniell’s 
pyrometer? Give the melting points of some of the most important met: 
als. Does the thermometer measure the heat to which it 1s exposed? 
W hat is it, then. that it does actually measure? What is meant by the 
intensity of heat? 


28 CAPACITY OF BODIES FOR HEAT. 


LECTURE VII. 


Capacity or Bopises ror Heatr.— Methods of determining 
Capacities. — Warming.— Melting.— Cooling.— Miz- 
ture-—Comparison between the Thermometer and Cal- 


orimeter.— Definition of Specific Heat. 


Many years ago it was discovered by Boyle, that if two 
bottles of the same size and form were filled with differ- 
ent liquids, and placed before the fire so as to receive its 
heat equally, their temperature did not rise similarly; 
thus, if one bottle was filled with water and the other with 
quicksilver, the temperature of the latter would rise much 
more rapidly than that of the former; and, on making 
the experiment with a little care, it will be found that the 

same quantity of heat will raise the temperature of mer- 
_ eury twice as high as that of an equal volume of water. 
By extending these experiments to other substances, it 
has been fully proved that different bodies require different 
amounts of heat to warm them equally. 

There are several different methods by which the ¢ 
pacity of bodies for heat may be determined, such as, 
by warming; 2d, by melting; 3d, by cooling; 4th, 
mixture. 

The first of these methods has already been 
by the experiment of Boyle. It consists. 
posing the same weight of the substance 
uniform source of heat, as, for example, a 
and examining how high their temperature 
given space of time. Thus it will be found 
twenty-three times as long to warm water as to warm 
mercury, when equal weights are used, and hence we 
infer that the capacity of water for heat is twenty-three 
times that of quicksilver. 

The second process is involved in the action of the cal 
orimeter, the operation of which may Vé easily under 
stood from J%g. 18. Take a solid block of ice, a a, in 
which a cavity of the form represented at 4 has been 


Describe Boyle’s experiment with water and quicksilver. To what 
general result do such experiments lead? State the different methods by 
which capacities for heat may be determined. Give an illustration of the 

. first process. 


THE CALORIMETER. 29 


made, and provide a slab of ice, ¢ ¢, Fig. 18. 
which may close completely the mouth 
of the cavity. Suppose it were re- , 
quired to determine the relative ca- y 
pacities of water and quicksilver for 
heat. In a glass flask, d, place one 
ounce of water, and by immersing |/77 
the flask in a bath of hot water, raise W/Z V7 
its temperature up to a given point, << 
as, for example, 200°; then place the flask at this tem- 
perature in the cavity 6, and put on the cover,cc. The 
hot water in the flask begins to cool, and in descending to 
82°, the point to which it will eventually come, a certain 

ortion of the surrounding ice is melted, the water re- 
sulting therefrom collects in the bottom of the cavity, and 
when the cooling is complete, it may be poured out and 
measured. 

In the next place, put in the flask one ounce of quick-. 
silver, the temperature of which is raised as before to 
200° by immersion in the hot-water bath; deposit the 
flask in the ice cavity, and put onthe cover. As the quick- 
silver cools, the ice melts, and when the collected water 
Ss measured, it is found to be less than in the other case, 
the proportion of 1 to 23. A given weight of water 
1 therefore melt 23 times as much ice as an equal 

ht of quicksilver, in cooling through the same number 


er of Lavoisier, which is represented in 
2 ; On the same prin- 
ciple as the block of ice. It 
consists of a set of tin vessels 
within each other; in the cen- 
tral one, a, the substance to be 
examined is placed, and be- 
tween this and the next vessel, 
at 6, the ice to be melted is 
introduced, broken into small 
fragments; the water arising 
from the melting flowing off 
through a stopcock, e, at the 


how how the capacities of water and mercury may be ascertained by 
the second. What are the relative capacities of equal weights of these 
bodies? Describe the calorimeter of Lavoisier. 


C2 


30 METHODS OF DETERMINING CAPACITIES. 


bottom into a measuring glass; and in order to avoid any 
portion of the ice being melted by the warm external air, 
another layer of fragments of ice is placed on the outside 
at d, and the water arising from it is carried off by a lat- 
eral stopcock, e. 

The third process, the method by cooling, known also 
as the method of Dulong and Petit, consists essentially in 
ascertaining the length of time required to cool threugh a 
given number of degrees. A substance which, like water, 
has a great capacity for caloric, and therefore contains a 
large amount of it, requires a greater length of time to 
cool; but one like quicksilver, the capacity of which is 
small, having less heat to give forth, requires a corre- 
sponding short space of time. The method by cooling re- 
quires several precautions; among others, the bodies un- 
der investigation should be placed in vacuo. It gives very 
exact results. 

The method by mixture may be readily understood. 
If a pint of water at 50° be mixed with a pint of water at 
100°, the temperature will be 75°, thatis the mean. But 
if a pint of mercury at 100° be mixed with a pint of wa- 
ter at 40°, the temperature of the mixture will be 60°: 
so that the forty degrees lost by the mercury can on. 
raise the temperature of the water twenty degrees. 
appears, therefore, that when equal volumes of these 


used, being then, as we have seen, in the He 
to 23. 

The method of mixtures is not limited to ot Inv estiva- 
tion of liquid substances, but it may also be extended to 
solids. Thus, ea pound of copper, heated to 300°, be 
plunged into a pound of water at 50°, the resulting tem- 
perature 1s 72°; from which it appears that the capacity 
of water for heat is about ten times as great as that of 
copper. 

By resorting to these various methods, the capacities 
of a great number of substances have been determined, 
and in the treatises on chemistry, tables exhibiting such 
results are given. But it will have been noticed, from the 


Describe the method of Dulong and Petit. Describe the method by 
mixture. Is this limited to liquid substances ? 


BLACK’S DOCTRINE OF CAPACITIES. 3l 


foregoing instances, that it is not the absolute quantities of 
heat in bodies that we thus determine, but only relative 
quantities in substances compared together. Such ta- 
bles require, therefore, one substance to be selected with 
which all the others may be compared, and for solids and 
liquids water has been chosen. Its capacity for heat is 
represented by 1°000, and with it they are compared. [or 
gaseous bodies atmospheric air is chosen. 

By contrasting the nature of the results given by the 
calorimeter, Fg. 19, with the indications of a thermom- 
eter, we shall see more clearly what it is that the latter 
instrument in reality points out. The calorimeter meas- 
ures quantities of heat, the thermometer intensities. As 
has been said, a thermometer placed in two vessels of 
different capacities, filled with water from the same source, 
will stand at the same height in both, and indicate the 
same temperature. But it needs no experiment to assure 
us that, if these different quantities of water were placed 
successively in the interior of the calorimeter, they would 
melt different quantities of ice, the one melting more of 
the ice in proportion to its greater weight compared with 
the other. 

_ Dr. Black, who was one of the early investigators of 
“these phenomena, introduced the term “Capacity of Bod- 
ant Heat,” implying the idea that this principle, enter- 
Ing their pores, could be taken up by different bodies in dif- 
_ ferent amounts. ‘Thus, if we have two pieces of sponge 
© of the same size, one of which is of a very dense, and the 
other of a porous texture, and cause them to imbibe as 
much water as they can hold, the porous sponge will of 
course contain the greater quantity. These sponges may 
therefore be said to have different ‘‘ capacities for water ;”’ 
-and this is precisely the idea which is conveyed in Black’s 
doctrine of capacity. 

But, upon these principles, it would follow that the 
lighter a body is, that is, the greater the interstices between 
its atoms, the more caloric it should be able to contain. 
Oil, therefore, which will float upon water, ought to have 
a greater capacity for heat than water; but, in fact, it is 


Do we thus determine the absolute qnantities of heat in bodies? What 
substance is used to compare solids and liquids? What is the substance 
for gases? How do the indications of the calorimeter compare with those 
of the thermometer? On what analogy is Black’s doctrine of ‘capacity’ 
founded? What is the objection to this doctrine ? 


az VARIATIONS OF SPECIFIC HEAT. 


the reverse, for its capacity, instead of being greater, is 
not one half. To avoid these difficulties, the term spe- 
cific heat has been introduced by most writers, and the 
term capacity abandoned, a change which I think is to 
be regretted. 

The specific heat of bodies, or their capacity for calor- 
ic, increases with their temperature. Upon Black’s doc- 
trine, the cause of this is readily understood, for, in sim- 
ple language, the pores become larger, and there is there- 
fore room for more heat. Solid substances, when violent- 
ly compressed, evolve a portion of their caloric: thus, a 
piece of soft iron, when hammered, becomes red hot. 
The doctrine of Black here again offers a ready expla- 
nation, for on the same principle that a sponge, when com- 
pressed, allows a certain portion of its water to exude, so 
the metalline mass, when its particles are forced together, 
allows some of its caloric to escape. 


LECTURE VIII. 


Capacity ror Hear anp Latent Heat.— Variability of 
Capacity under Compression and Dilatation — Theory of 
the Formation of Clouds— The Fire Syringe.—Cold in 
the upper Regions of the Air.—Connection between Spe- 
cific Heats and Atomic Weights.——Latent Heat—Ca- 
loric of Fluidity. = 


Wuen the volume of a gas increases, its capacity for 
heat increases, and a diminution of volume is attended 
with a diminution of capacity. Thus, if we 
place a Breguet’s thermometer under the re- 
ceiver of an air pump, and exhaust rapidly, a 
sudden reduction of temperature is indicated, 
arising from the fact that, as the rarefaction is 
\ effected, the capacity increases, an increase 
which is satisfied at the expense of a portion of 
the sensible heat. 

Upon the same principle we can explain the sudden 


What is meant by specific heat? Does the capacity of bodies change 
with their temperature? Does it-change under compression? How is 
this explained agreeably to Black’s doctrine? When the volume of a 

as changes, what are the changes in its aes heat? What is the 

ct which the experiment of Fig. 20 proves 


FORMATION OF A CLOUD. 33 


appearance of a fog or cloud, when moist air is quickly 
rarefied. It will be seen, when I come to speak of the 
nature of vapors, that the quantity of vapor which can 
exist in a given space depends on the temperature; thus, 
if a space saturated with vapor is cooled, a portion of the 
vapor assumes the liquid form. When, therefore, by 
the aid of an air pump, we suddenly rarefy air saturated 
with moisture under a receiver, the capacity increases, 
cold is produced, and a part. of the water takes on the 
form of drops. It is on this principle that the 
nephelescope acts: it consists of a receiver, a, 
Fig. 21, connected with a flask, c, by an inter- 
vening stop-cock,4; the stop-cock being closed, 
the receiver is exhausted by the pump, and 
now, on suddenly opening the stop-cock, so that 
the air contained in the flask may rapidly ex- 
pand into the receiver, a mist or cloud makes 
its appearance, due to the deposit of water in 
the form of minute drops. Ifthe air at the time 
be very dry, it may be purposely rendered 
emoist by being exposed to water. 

When atmospheric air is suddenly compressed, its ca- 

pacity for heat diminishes; this is well shown by fig.22. 
an instrument such as is represented in Fg. 22, 
consisting of a syringe, with a piston moving per- 
-fectly air tight in it. On the end of the piston 
there is an excavation, in which a piece of tinder 
may be fastened; the piston being rapidly forced 
into the syringe, the air is compressed, the capacity 
for heat becomes less, caloric is evolved, and the 
tinder set on fire. At one time these syringes were 
used as a means of obtaining fire. 

The variation in capacity of substances under variation 
of volume may be clearly understood and readily borne 
in mind by Black’s doctrine, as illustrated in the case of 
a moistened sponge. If a sponge which has imbibed as 
much water as it can hold be compressed, a portion of 
the water exudes, just as the air in the syringe allows a 
portion of its heat to escape when pressure is made. On 


What is the theory of the production of clouds? Describe the nephel- 
escope. What is the result of the action of this instrument? When air 
is compressed, why does it emit heat? How can these changes be ac- 
counted for by Black’s doctrine ? 


34 SENSIBLE AND INSENSIBLE HEAT. 


relaxing the force on the sponge, and allowing it to dilate, 
it will take up an increased quantity of water ; ; and air, 
when suddenly dilated, as we have seen, has its capacity 
for heat increased. 

From these facts, it appears that the heat of bodies 
exists under two different forms, as sensible and insensible 
heat. In the experiment with the syringe, just related, 
the heat that sets fire to the tinder existed previously to 
compression in the air; it existed as insensible heat, but 
during the compression it put on the form of sensible heat. 
The same transition is also recognized in the action of the 
nephelescope; the heat, which was sensible before rare- 
faction, becomes insensible, and cold, or a depression of 
temperature, is the result. 

The great degree of cold which reigns in the upper 
regions of the atmosphere is due, to a considerable extent, 
to the capacity of that dilated air for heat. On the same 
principle we can explain the formation of clouds from 
transparent atmospheric air: a stratum of air, reposing on 
the surface of the sea, or the moist earth, becomes satu- 
rated with vapor; by the warmth of the sun or other 
causes, it begins to rise in the atmosphere, and as it rises: 
it expands, because the pressure upon it is continually 
becoming less. An increased capacity is the result of its 
dilatation, and, as is the case in the nephelescope, cold is 
produced, and a deposit of a part of the moisture takes 
place; this moisture, appearing under the form of minute 
drops, is what we call a cloud. 

IF’rom the small capacity of quicksilver for heat, we see 
one of the reasons that it 1s a suitable substance for form- 
ing thermometers; it warms rapidly and cools rapidly, 
and therefore follows variations of temperature much more 
promptly than water and most other liquids. 

There is a connection between the specific heat of sev- 
eral simple bodies and their atomic weights, pointing out 
the fact that elementary atoms have in many instances 
the same specific heat; recently the same conclusion has 
been established in the c case of certain oxides, carbonates, 
and sulphates. 


What are the relations between sensible and insensible heat? De- 
scribe the mode in which clouds form. Why does the capacity of quick- 
silver fit it for a thermometric liquid? What is the relation of the specitic 
heat of many elementary bodies ? 


LATENT HEAT. 35 


If we take a mass of ice, the temperature of which is at 
the zero point, and bring it into a warm room, examining 
the circumstances under which its temperature rises, they 
will be found as follows: the mass of ice, like any other 
solid body, warms with regularity until it reaches 32°; 
then, for a considerable period of time, no farther eleva- 
tion is perceptible, but it undergoes a molecular change, 
assuming the liquid condition; when this is complete, the’ 
temperature again commences to rise. 

That we may have precise views of these facts, let us 
suppose that the mass of ice and the warm room into 
which it is carried have such relations to each other that 
the temperature of the former can rise from the zero point 
one degree per minute; for thirty-two minutes the tem- 
perature of the ice will be found to increase, and at the 
end of that time, a thermometer, if applied, would stand 
‘at 32°, But now, although the heat is still entering the 
ice at the rate of a degree per minute, the process of 
warming ceases, and for 140 minutes no farther rise takes 
place; the ice now commences to melt, and in 140 min- 
utes the liquefaction is complete. The temperature then 
again rises, and continues to do so with regularity. 

We infer from results like the foregoing, that about 
140 degrees of heat are absorbed by ice in passing into 
the condition of water; and as this heat is not discoverable 
by the thermometer, it is designated as latent heat. 

A similar fact appears when any liquid, such as water, 
passes into the gaseous or vaporous condition. Thus, if 
some water be exposed to a fire which can raise its tem- 
perature at the rate of one degree per minute, that effect 
will continue until 212° are reached; at that point, no mat- 
ter how much the heat be increased, the temperature re- 
mains stationary. The water undergoes a change of form, 
assuming the condition of a vapor, and the change is com- 
pleted in about 1000 minutes. In this, as in the former 
instance, we infer that a large amount of heat has become 
latent, or undiscoverable by the thermometer, and that it 
is occupied in establishing the elastic form which the 
water has assumed. 


Describe the change which ice undergoes when warming. Is there any 
pause in the elevation of its temperature? How many degrees of heat 
are absorbed during the liquefaction of ice? What is latent heat? How 
many degrees of heat are absorbed during the vaporization of water? 

What is the latent heat of steam? 


36 CALORIC OF FLUIDITY. 


The caloric which thus disappears when a solid as- 
sumes the liquid form, takes also the designation of caloric 
of fluidity, and that which disappears in the formation of 
a vapor, the caloric of elasticity. 

In the treatises on chemistry, tables may be found ex- 
hibiting the caloric of fluidity of different bodies; thus, 
the caloric of fluidity of water is 140°, that of melted lead 
162°, of bees’ wax 175°, and of melted tin 500°. 

By the method of mixtures the same results may be es- 
tablished; thus, if a pound of water at 32° is mixed 
with a pound at 172°, the mixture will have the mean 
temperature, that is, 102° ; but if a pees of ice at 32° 
be mixed with a pound of iter at 172°, the mixture still 
remains at 32°, and the reason is clear, from the foregoing 
‘considerations, that ice in passing into the liquid state ‘re- 
quires 140° of caloric of fluidity which is rendered latent. 


LECTURE Ix. 


‘Latent Heat.—Heat evolved in Solidification— Theory 
of freezing Mixtures.—Expansion during Solidification. 
—Fixity of the Melting Point— Latent Heat connected 
with the Duration of the Seasons— Nature of Vapors. 
— Caloric of Elasticity. "5 


Wuen a liquid assumes the solid form, a considerable 
amount of heat is evolved. ‘The cause is readily under- 
stood, from what we have seen taking place during the 
reverse process; which has led us to the fact that the 

Fig. 23, difference between any given solid and the 
liquid which arises from it by melting is in 
the large amount of latent heat which is found 
in the latter, and which is occupied in giving 
it its form. 

A saturated solution of sulphate of soda 
may be cooled from its boiling point to com- 
| mon temperatures, in a vessel tightly corked, 
# ~ without solidification taking place ; but when 
the cork is withdrawn crystallization ensues, 


What is caloric of fluidity? What is caloric of elasticity? How can 
the doctrine of latent heat be established by the method of mixtures? Is 
heat absorbed or evolved when a liquid solidifies? What is the cause of 
this? How can it be illustrated with a solution of sulphate of soda? 


FREEZING MIXTURES. 37 


and heat is evolved. This may be proved by taking a 
bottle, a a, Fg. 23, filled with such a solution ; and having 
introduced the bulb of an air thermometer through the 
neck, 6, by means of an air-tight cork, the mouth, ¢, of 
the bottle is to be carefully stopped. When the whole 
apparatus has reached the ordinary temperature of the 
air, the stopper at c is withdrawn, and solidification at 
once takes place, or, if it should at first fail, the introduc- 
tion of a crystal of sulphate of soda will bring it on. At 
that moment it will be perceived, that not only does the 
thermometer indicate a rise of temperature, but if the bot- 
tle be grasped, it will be found to be sensibly warm. — 

With care, water may be cooled to a point far below 
that of freezing without assuming the solid form. If, un- 
der these unusual circumstances, it be agitated, solidifica- 
tion ensues, and heat is evolved, the temperature rising to 
ae. 

On these principles depends the action of freezing mix- 


tures, of which the following is an example: If we take | 


eight parts of crystallized sulphate of soda, and mix it ina 
thin tumbler with five parts of hydrochloric acid, the sul- 
phate of soda, from being a solid, assumes the liquid form ; 
and taking, in order to effect that change of form, caloric 
from surrounding bodies, it reduces their temperature. 
This may be shown by placing four parts of water in a 
thin glass test tube, and stirring it about in the mixture ; 
the water speedily freezes, even though the experiment 
may be made on a warm summer day. 

In the treatises on chemistry tables of freezing mixtures 
are inserted. All these mixtures depend essentially on 
the principle under consideration—that latent heat must 
be furnished to a substance passing from the solid to the 
liquid state. They consist of various solid substances, the 
liquefaction of which is brought about by the action of 
other bodies; thus, in the instance we have seen, the sul- 
phate of soda is brought from the solid to the liquid state 
by muriatic acid, and heat is necessarily absorbed. Into 
the composition of many of the most effective of these 
freezing mixtures ice or snow enters. Thus, a mixture 
of snow and common salt will bring the thermometer be- 


Can water be cooled below 32° without freezing? Give an example 
of a freezing mixture. What are the principles on which freezing mix 
tures act? 
D 


Din 


38 SOLIDIFICATION OF WATER. 


low the zero point, and when nitric acid is poured on 
snow, the temperature falls as low as thirty degrees be- 
low zero. 

Many substances, when solidifying, expand. This is the 
case with water, in which the amount of expansion is about 
Ith of the bulk. The force which is exerted under these 
circumstances is very great, and capable to tearing open 
the strongest vessels. Onasmall scale, this may be easily 
shown by filling a bottle full of water, and, having intro- 
duced the cork, fastening it tightly down with a piece of 
wire. On putting such a bottle into a freeaing mixture, 
for example, snow moistened with nitric acid, congelation 
promptly takes place, and the bottle is burst. 

The freezing point of water is usually spoken of as a 
fixed point, and is marked as such upon the scales of our 
thermometers ; but if water be cooled without allowing 
any movement or agitation of its parts, it may be brought 
as low as 15°. It is then in the same condition as the 
saturated solution of sulphate of soda just alluded to. 
The slightest motion is sufficient to solidify it. But though 
water will retain its liquid form far below its freezing 

oint, ice can not be brought above 32° without melting. 
Ther melting of ice, and not the freezing of water, is there- 
fore the fixed thermometric point. 

We have seen that the possession of a point of maxi- 
mum density by water exerts a great effect upon the du- 
ration of the seasons: a similar observation might be made 
as respects its latent heat. If ice, by the absorption of a 
single degree of heat, when it passes from 32°, could 
turn into water, the great deposits of winter would sud- 
denly melt, and inundations be frequent; or, if water, by 
losing a single degree of heat, turned into ice, freezing 
would go on with great rapidity. To the melting of ice, 
or the freezing of water, time is necessary; the 140° of 
latent heat have to be disposed of; this, therefore, serves 
to procrastinate the approach of winter, and causes the 
spring to come forward with more measured steps. In 
autumn the water has 140° degrees of heat to give out to 


What is the amount of the expansion of water in the act of freezing? 
How may the force with which this expansion takes place be illustrated ? 
Is the freezing point of water a fixed thermometric point? How low can 
water be cooled without freezing? Is the melting of ice, or the freezing 
of water, the fixed thermometric point? What connection has the latent 
heat of water with the duration of the seasons? 


. 


PROPERTIES OF VAPORS. 39 


surrounding bodies before it solidifies; in spring it must 
receive the same amount before it will melt. This, there- 
fore, serves as a check upon sudden changes in the seasons. 

Having thus discussed the leading facts observed in the 
change from the solid to the liquid condition, let us now 
turn our attention to the second change of form, the pass- 
age from the liquid to the gaseous state. 

A technical distinction is made between a gas and a 
vapor; by the latter, we understand a gas which will 
readily take on the liquid form. 

Some of the leading peculiarities in the constitution of 
vapors may be exhibited by the following Fig. 24. 
experiment: Take a glass tube,aa, Ig. fa > 
24, with a bulb, 4, blown on its upper ex- 
tremity; pour water into the bulb, filling 
the tube to within an inch or two of the 
end; this vacant space fill with sulphuric 
ether; and now, closing the end of the tube 
with the finger, invert it in a glass of wa- 
ter, as is represented in the figure. The ether, being 
much lighter than water, at once rises to the upper part 
of the bulb, as is shown by the light space, the bulb being 
of course full of ether and water conjointly. 

On the application of a spirit lamp the ether vaporizes, 
and presses the water out of the bulb into the glass cup. 
Three important facts may now be established. 

lst. Vapors occupy more space than the liquids from 
which they arise. 

_ 2d. They have not a misty or fog-like appearance, but 
are perfectly transparent. 

_ 3d. When their temperature is reduced, they collapse 
to the liquid state. 

That the first of these observations is true, is at once 
seen on comparing the quantity of ether with the volume 
of vapor which has risen from it; the ether occupying but 
a small space at the top of the bulb, the vapor fills it en- 
tirely. We perceive, moreover, that ethereal vapor does 
not possess that cloudy appearance which is popularly at- 
tached to the term vapor, but that it is as transparent as 


What is the distinction between a gas and a vapor? Describe the ex- 
periment represented in Fig. 24. What is the difference between a va- 
por and the liquid which:forms it, as to volume? Have vapors necessari- 
y a cloudy appearance ? 


40 VAPORIZATION. 


atmospheric air. And, on removing the lamp, so that the 
temperature may fall, the liquid rushes up violently into 
the bulb, exhibiting the ready collapse of the ether vapor 
into the condition of a liquid. 

We have already proved that a large amount of heat 
becomes latent, constituting the caloric of elasticity of va- 
pors. The temperature of steam is 212°, as is that of the 
water from which it rises; but it contains about 1000° 
of latent heat, which gives to it its new form. Different 
vapors possess different quantities of latent heat; thus, for 
ether the number is 163°, for alcohol 376°, and, as we 
have said, for water 1000°; that is enough, were it a 
solid, to make it visibly red hot in the daylight. 


LECTURE X. 


VaporizatTion.— Vapors form at all Temperatures — 
Form instantly nm a Void—kEffects of removing Pres- 
sure.— Measure of Elastic Force of Vapors.—Cumula- 
tive Pressure. Failure of Marriotte’s Law.—Elasticity 
encreases with Temperature—Maximum Density of Va- 
pors. 


VaprorizaTIoNn goes on at all temperatures. It is not 
Fig.25. | necessary that the boiling point should be 
reached ; even ice will evaporate away. The 
thin films of this substance often seen incrust- 
ing glass windows may disappear without un- 
dergoing the intermediate process of fusion, 
and a mass of ice freely exposed to the air on 
a dry, frosty day, loses weight. Steam, there- 
fore, rises from water at all temperatures, but 
with more rapidity and a higher elastic force 
as the temperature is higher. 

In a vacuum vapors form instantaneously. 
If we take a barometer, a@ a, Pig. 25, and 
pass intothe Torricellian vacuum which ex- 


On reduction of the temperature, what phenomenon do they exhibit? , 
How are these three facts proved? What is the amount of caloric of 
elasticity of steam? Mention it also in the case of ether and alcohol. 
How can it be proved that vaporization goes on at all temperatures ? 
What is the effect which ensues when a vaporizable liquid i is passed into 
a Torricellian vacuum ? 


EFFECTS OF CHANGE OF PRESSURE. 41 


ists at its upper part, a small quantity of sulphuric ether, 
even before it has reached the void space, vapor forms, 
and the mercury is instantly depressed. Under ordinary 
circumstances, when the instrument, as at 6 6, is standing 
at 30 inches, the column at once falls to 15 or 16, the 
space being now filled with the vapor of ether; and if in 
succession other liquids are tried, the same general result 
is obtained—instantaneous vaporization ; but the amount 
of vapor set free is different in the different cases. 

Diminution of atmospheric pressure is, therefore, favor- 
able to vaporization, and were the pressure of the air en- 
tirely removed, there are many liquids which would as- 
sume a permanently aerial form. Let a, Pig. 26, be a 
glass bottle, into the neck of whicha funnel, pe. 96, 

6 b, is ground air-tight; the bottle is to be C 
filled with quicksilver, except a small space 
at its upper part, which is occupied by sul- 
phuric ether. If this instrument be placed 
beneath the receiver of an air pump, as soon 
as exhaustion is made, the mercury will be 
seen rising into the funnel, and its place tak- 
en by the transparent vapor of ether. As 
long as the reduction of pressure continues, | 
the ether keeps the gaseous form, but on re- « 
admitting the air, it returns to the liquid 
state. By increase of pressure, as well as by diminution 
of temperature, vapors may be reduced to the liquid con- 
dition. 

Though the law that vapors occupy more space than 
the liquids from which they come is of universal applica- 
tion, the increase of volume is by no means the same in 
all cases. Under ordinary circumstances of pressure, a 
cubic inch of water at its boiling point produces nearly a 
cubic foot of steam, or 1696 cubic inches, more accurate- 
ly. ‘The same quantity of alcohol produces 519 cubic 
inches, and of oil of turpentine 192 cubic inches. 

The elastic force exerted by vapors under certain lim- 
its can be measured by the apparatus given in Pg. 25. 
The theory of the process is very simple. The height at 


a) on 


What substances exist commonly in the liquid state, in consequence of 
the pressure of the air?) What is the effect of an increased pressure on 
vapors? Do all liquids expand equally in assuming the vaporous state ? 
How can the elastic force of soa be measured by the barometer ? 

9 


te 


A2 CUMULATIVE PRESSURES. 


which the barometer stands is determined by the pressure 
of the air. In the experiment there described, as long as 
there is nothing to counterbalance that pressure, the mer- 
cury is forced up by it in the tube to a height of 30 inch- 
es; but on introducing some ether, the vapor which 
forms, exerting an elastic force in the opposite direction, 
tends to push the mercury out of the tube. On the one 
hand, we have the pressure of the air; on the other, the 
elastic force of the ethereal vapor; they press in opposite 
directions, and the resulting altitude at which the mercury 
stands expresses, and, indeed, measures the elastic force 
of the vapor. Thus, at a temperature of eighty degrees, 
water will depress the mercurial column about 1 inch, al- 
cohol about 2 inches, and sulphuric ether about 20. These 
numbers, therefore, represent the elastic force of the va- 
pors evolved. 
Fig. 27. In close vessels, from which there is no 
a escape, or where the escape is greatly re- 
XY’ tarded, a constantly accumulating force is 
’ generated, when the temperatureis raised. 
Thus, if we place some water in a flask, 
a, Fig. 27, into which a tube, b 3, is in- 
serted air-tight by means of a cork, and 
bent in the form exhibited in the figure, 
and dipping nearly to the bottom of the 
flask ; on the application of a spirit lamp, 
the vapor generated, having no passage 
of escape, accumulates in the upper part of the flask, and, 
Fig. 28. exerting its elastic force, presses fie 
liquid through the tube in a continu- 
ous stream. The mechanical force 
which thus arises, when every avenue 
of escape is stopped, is strikingly ex- 
hibited by the little glass bulbs called 
candle bombs; these are small glob- 
ules of glass, about as large as a pea, 
: with a neck an inch long; into the in- 
terior a drop of water is introduced, and the termination 
of the neck hermetically sealed by melting the glass. 
When one of these is stuck in the wick of a candle or 


—— 


What is the principle involved? When water is heated in a vessel 
from which the steam can not escape, whatis the effect? How may this 
v; illustrated 7 


RELATION OF VAPORS TO PRESSURE. 43 


lamp, as in Fg. 28, the heat vaporizes a portion of the 
water, and there being no passage through which the steam 
can escape, the bulb is burst to pieces with a loud explo- 
sion; a mechanical force which is wonderful when we 
consider the amount of water employed. It is a minia- 
ture representation of what takes place on the large scale 
in the bursting of high-pressure steam-boilers. 

Marriorte’s law, the law which assigns the volume of 
a gas under variations of pressure, applies, under certain 
restrictions, to the case of vapors. A permanently elas- 
tic gas, when the pressure is doubled, contracts to one half 
of its former volume; if the pressure be tripled, to one 
third, and so on, but not so with vapors; if, upon steam, 
as it rises from water at 212°, any increase of pressure 
be exerted, this vapor at once loses its elastic form, and 
instantly condenses into water. But vapors, like atmo- 
spheric air, if the pressure upon them is diminished, fol- 
low Marriotte’s law; thus, if the pressure be reduced to: 
one half, steam at once doubles its volume. Jor vapors, 
therefore, Marriotte’s law holds for diminutions of press- 
ure, but in other instances, when the pressures are in- 
creased, it apparently fails, the vapors relapsing into the 
liquid form. 

That the elasticity of a vapor increases with its temper- 
ature, may be readily proved by taking a tube one py, 99, 
third of an inch in diameter and 12 inches long, 
closed at one end and open at the other, aa, Fig. 29, 
with ajar, 6, an inch or more in gees and 12 
inches deep. Let the tube be filled with quicksil- 
ver, so as to leave a space of half an inch, into which 
ether may be poured; invert the tube in the deep 
jar, also containing quicksilver; the ether of course 
rises to the upper closed extremity. I’ now the 
tube be lifted in the jar as high as possible without 
admitting external air, a certain portion of the ether 
will vaporize, and, depressing the quicksilver, its elastic 
force may be measured by the length of the resulting 
column. If now the end of the tube be erasped in the 
hand, or if it be slightly warmed by the application of a 


What is Marriotte’s law? Does it apply in the case of vapors under a 
diminution of pressure? Does it apply under an increase? What rela- 
tion is there between elasticity.and temperature? How can the increase 
of elastic force under these circumstances be shown? 


44 MEASURE OF ELASTIC FORCE. 


lamp, the mercurial column is at once depressed, proving 
that the elastic force of the vapor is increasing. As soon 
as the tube is warmed to the boiling point of the ether, 
the column of mercury is depressed exactly to the level 
on the outside of the tube. At this point, therefore, it bal- 
ances, or is equal to the pressure of the air. 

Now let the tube be depressed in the jar; it will be 
seen with what facility the vapor reassumes the liquid 
condition. As the tube descends, the vapor condenses, 
and the mercury keeps constantly at the same level. 

Under these circumstances, it follows that the vapor 
is at its maximum density. We can not increase that 
density by bringing pressure to bear upon it by depress- 
ing the tube, for the moment the attempt is made the 
vapor liquefies. 


LECTURE XI. 
Exsvuuuition.— Theory of Boiling. —In Papin’s Digester 


Water never Boils— Instantaneous Condensation of Va- 
pors.—Liffect of Variations of Pressure.—Effect of Na- 
ture of the Vessel.— Bowling on Mountains —Liffect of 
fted-hot Surfaces. 


By introducing different liquids into a tube, arranged 
as that represented in Fvg. 29, we can prove that the ob- 
servation holds good in every case, that, as soon as the 
boiling point of a liquid is reached, the elastic form of the 
vapor rising from it is equal to the pressure of the air. 

We have said that at a temperature of 80° the vapor of 
water will depress the mercurial column of a barometer 
about one inch, but if the temperature be raised to 2129, 
the mercury is at once depressed to the level in the cistern; 
at that temperature, therefore, the elastic force of the 
vapor is equal to the pressure of the air. 

Upon these principles, the phenomena of boiling or 
ebullition are easily explained. When the temperature 
of a liquid is raised sufficiently high, vapor is rapidly gen- 

At the boiling point of a liquid, what is the elastic force of its vapor 
equal to? What is meant by the maximum density of a vapor? How 
can it be shown that vapors thus in a Torricellian void are at the maxi- 


mum density? At the boiling point of water, what is the elastic force of 
its steam? Explain the phenomena of boiling. 


BOILING, 45 


erated from those portions of the mass which are hottest, 
and the violent motion characterized by the term“ boiling” 
is the result. This is due to the fact that the elastic force 
of the generated vapor at that point is equal to the at- | 
mospheric pressure, and the vapor bubbles expanding, 
can maintain themselves in the liquid without being crush-~ 
ed in; they rise to the surface, and there burst. But, 
just before ebullition takes place, a singing sound is often 
heard, due to the partial formation of bubbles, which, so 
long as they are in the neighborhood of the hottest part, 
have elasticity enough to maintain their form; but the 
moment they attempt to rise through the cooler portion of 
the liquid just above, their elasticity is diminished by 
their decline of temperature, and the atmospheric pressure 
crushing them in, they resume the liquid condition; for 
a few moments, therefore, while the vapor has not gath- 
ered elastic force enough to maintain its condition per- 
fectly, these bubbles are transiently formed and disappear, 
and the liquid is thrown into a vibratory movement which 
gives rise to the singing sound. 

Water, when heated in a vessel from which the steam 
can not escape, never boils. This takes place in the inte- 
rior of Papin’s digester, which is a strong metallic vessel, 
in which water is enclosed, and the orifice through which 
it was introduced fastened up. As the steam can not es- 
cape, the water can not boil, no matter what the tempera- 
ture may be. But the vapor which accumulates in the in- 
terior of the vessel exerts an enormous pressure. It is 
under the same conditions as were considered in the case 
of the candle bombs. Papin’s digest- 
er is used to effect the solution of bod- 
ies by water which are not acted on 
readily by that liquid at its common 
boiling point. 

As a vapor, rising from a vaporizing / 
liquid, will bear no increase of press- aff 
ure, so neither will it bear any reduc- \ 
tion of temperature without instanta- 
neously condensing. This may be 
strikingly shown by an arrangement 


F gz. 30. 


What is the cause of the singing sound? Why does water heated in 
a close vessel never boil? Describe Papin’s digester. What is its use? 
Can the steam of boiling water be cooled without condensation ? 

2% 


46 RAPIDITY OF CONDENSATION. 


such as is represented in Ig. 30. Into the mouth of a 
flask, a, let there be fitted a tube, 4, half an inch in diam- 
eter, and bent, as shown in the figure. Having introduced 
a little water into the flask, cause it to boil rapidly by the 
application of a spirit lamp: the steam which forms soon 
drives out the atmospheric air from the flask and the 
tube, and when this is entirely completed, and the vapor 
issuing abundantly from the mouth of the tube, plunge 
the end of the tube beneath some cold water contained in 
the jar, c, and take away the lamp. As soon as this is 
done, the cold water, condensing the steam in the tube, 
rises to occupy its place ; and presently passing over the 
bend, introduces itself with surprising violence into the 
interior of the flask, filling it entirely full, or, which more 
commonly takes place, breaking it to pieces with the force 
of the shock. The low-pressure steam-engine depends on 
this fact of the rapid condensibility of vapor, the high- 
pressure engine on its elastic force. 

Fig. 31. The principle involved in the action of 
the low-pressure engine, and more espe- 
cially that form of it which was the inven- 
tion of Newcomen, is well illustrated by 
the instrument represented in /ig.31. It 
consists of a glass tube, blown into a bulb 
at its lower extremity. In the bulb some 
water Is placed, and a piston slides, with- 
out leakage, in the tube. On holding the 
bulb in the Gara of a spirit lamp, steam is 
generated, and the piston forced upward. 
On dipping it into a basin of cold water, 
the steam condenses and the piston is de- 
pressed ; and this action may be repeated 
at pleasure. 

As the pressure of the atmosphere determines the boil- 
ing point of a liquid, and as that pressure is variable, the 
baling point is not a fixed, but a variable point. There 
are many experiments which might be introduced as proofs 
of this fact. Ifa glass of warm water be placed beneath 
the receiver of an air pump, as in Fig. 32, when the 


Give an example of the rapidity of its condensation. On what proper- 
ty of vapor does the low-pressure steam-engine depend? On what, the 
high-pressure ? How may it be proved that the boiling point depends on 
the pressure ? iil 


Pay 
a 
Ve 


BOILING IN VACUO. 47 


rarefaction has reached a certain point, ebul- 
lition sets in, and the water continues to boil 
at alower temperature as the exhaustion is 
more perfect. In a vacuum, water can be 
made to boil at 67°. 

On this principle, that the boiling point de- 
pends on the existing pressure, we give an 
explanation of a curious experiment, in 
which ebullition is apparently brought about 
by the application of cold: Take a Flor- 
ence flask, a, Fig. 33, and, having filled 
it half full of water, cause the water to. 
boil violently, so as to expel all the atmos- 
pheric air; introduce a cork which will fit 
the mouth of the flask air-tight, a mo- — 
ment after it is moved from the lamp, and before any 
atmospheric air has been introduced. If the flask be 
now dipped into a jar, 4, of cold water, its water be- 
gins to boil, and will continue to do so eel its tempera-: 
ture is reduced quite low. ‘The cause of this phenomenon 
is due to the fact, that the cold water condenses the steam 
in the flask, and a partial vacuum is the result. In this 

artial vacuum the water boils, as in the experiment il- 
lustrated by Fig. 32; and the steam, as fast as it is gen- 
erated, is condensed by the cold Blok of the flask. 

hades this variation of the boiling point under varia- 
tion of pressure, the nature of the vessel in which the pro- 
cess is carried forward exerts a certain action ; thus, in a 
polished glass vessel the boiling point is 214°, but in a - 
rough metal vessel it is 212°. ' 

Some travellers report, that in certain mountainous re- 
gions meat can not be cooked by the ordinary process of 
boiling. As we ascend to elevated regions in the air, the 
atmospheric pressure becomes less, because the column 
of air above is shorter, and therefore there is less air to 
press. Under such circumstances, the boiling point of 
water of course descends, and may possibly become so 
low as to be unable to bring about the specific change re- 
quired in the cooking of meat. An ascent through 530 


At what temperature will water boil in vacuo? Explain the process 
by which warm water may be made to boil by the application of cold? 
How does the nature of the vessel affect the boiling poimt? Why is it 
probable that meat can not be cookedaag bigh mountains ? 

¥ , 


a8 


GG 


48 LIQUIDS ON RED-HOT SURFACES. 


feet lowers the boiling point one degree. Upon this prin- 
ciple we can determine the altitude of accessible eleva- 
tions, by determining the thermometric point at which 
water boils upon them. A peculiar thermometer, called 
the hypsometer, has been invented for this purpose. 

When a drop of water is placed on a red-hot polished 
surface of platinum, it does not, as might be expected, 
commence to boil rapidly, but remains perfectly quiescent, 
gathering itself up into a globule. If the platinum be 
now allowed to cool, as soon as its temperature has reach- 
ed a point at which it ceases to be visibly hot, the drop 
of water is suddenly dissipated in a burst of steam. 
The explanation given of this phenomenon is, that at the 
high temperature the drop is not fairly in contact with the 
red-hot surface, but a stratum of steam intervenes; this, 
being a bad conductor, prevents ebullition from occurring, 
but as soon as the temperature declines, and this steam 
no longer props up the drop, an explosive ebullition en- 
sues, because of the contact which has taken place. 


LECTURE XII. 


VaporizatTion.— The Boiling Point rises with the Press- 
ure.—Relation between sensible and insensible Heat.— 
The Cryophorus.—Leslie’s Process for freezing Water. 
— Variability of Moisture in the Aw.— Hygrometers.— 
Method of the Dew Point. 


Unpber an increase of pressure, the boiling point rises, 
and the elastic force of the steam evolved becomes corre- 
spondingly greater, As we have seen, the elastic force of 
steam from water boiling at 212° is equal to the press- 
ure of one atmosphere ; but if the pressure be doubled, 
the boiling point rises to 250°; if quadrupled, to 294°; 
and under a pressure of fifty atmospheres, it is more than 
500°. 


How high must we ascend to bring the boiling point to 2119? How 
may the altitude of mountains be determined by the thermometer ? 
V¥hat are the phenomena exhibited by water in contact with red-hot 
platinum? What is the supposed explanation? How is the boiling 
point affected by an increased pressure 7 


Be RON 


eer 
rie 


LATENT HEAT OF VAPORS. 49 


» 


- These results may be established by the 
aid of the boiler, represented in Mg. 34, 
a. It is a globular vessel of brass, and is 
about three inches in diameter. In its up- 
per part are three perforations, into one of 
which the stop-cock, 4, is screwed ; through 
the second a tube,c, is inserted, deep enough 
to reach nearly to the bottom of the boiler; 
and through the third a thermometer, d, 1s 
introduced. Some quicksilver is poured 
in, sufficient to cover the end of the tube, 
c, half an inch or more deep, and upon it 
water is poured, the bulb of the thermometer being im- 
mersed in it. The stop-cock, 4, being open, a spirit lamp 
is applied to bring the water to its boiling point, and as 
the steam can freely pass out, this of course takes place 
at 212°. On closing the stop-cock, the steam can no lon- 
ger escape, but exerting its elastic force on the surface of 
the boiling liquid, presses the mercury up in the tube, c. 
The altitude of the mercurial column measures the amount 
of this pressure, and the thermometer indicates the corre- 
sponding change in the boiling point: as soon as the press- 
ure is equal to two atmospheres, the thermometer will 
be found to have risen to 250°. 

It is immaterial at what temperature vaporization is 
carried on, a very large amount of heat must always be 
rendered latent; and, in point of fact, vapors generated at 
a low temperature contain more latent heat than those 
generated at a high one. The relation which exists in 
the amount of heat rendered latent at different tempera- 
tures is very simple. The sum of the insensible and 
sensible heat is always the same; thus, water boiling at 
212° absorbs 1000° of latent heat, the sum of the two 
quantities being of course 1212°; but vapor rising from 
water at 32° contains of latent heat 1180°; here, again, 
the sum of the two quantities is 12129; and the same ob 
servation holds for intermediate temperatures. 

‘When vapors return to the liquid condition, the heat 
which has been latent in them reassumes the sensible 


Describe the boiler, Fig. 34, and its use. Do vapors generated at low 
or high temperatures contain most latent heat? ‘What relation is there 
between the insensible and sensible heats of vapors at different tempera- 
tures? When a vapor condenses, what becomes of its latent heat? 


=> 


ad 


50 THE CRYOPHORUS. 


form. They may thus be regarded as containing a great 
store of caloric, of the effects of which many natural phe- 
nomena furnish us with striking examples. Thus, there 
is a remarkable difference between the climate of the 
eastern coast of America and the opposite European 
coasts in the same latitude, and this arises from the action 
of the Gulf Stream, a great stream of warm water, which, 
issuing from the Gulf Ag Mexico, and passing the Atlantic 
States, stretches across toward the European Continent. 
The vapors which arise from it give forth their latent heat 
to the air, and the southwest winds, which are therefore 
damp and warm, moderate the climates of those coun- 
tries. 

The cryophorus, or frost bearer, an instrument invent- 

Fig. 35. ed by Dr. Wollaston, in which water may be 
>\ frozen by the cold produced by its own evapo- 
'(@ ration, depends for its action on the laws re- 
lating to latent heat. It is represented in I’vg. 
35, and consists of a bent tube, c, half an inch 
or more in diameter, with a bulb, @ and 4, at 
each of its extremities; the upper bulb, 4, is 
filled one third with water, and the rest of 
the space, with the tube, c, and the other bulb, 
a, is free from atmospheric air, and occupied by 
the vapor of water only. If, now, the bulb @ be 
immersed in a freezing mixture of nitric acid and snow, 
although the tube, c, may be of considerable length, the 
water in the distant bulb, 5, presently freezes; hence the 
name of the instrument, frost bearer, because cold applied 
at one point produces a freezing effect at another, which 
is at a considerable distance. The action of the instrument 


is simple: in the cold bulb, a, which eel Tesh with 


the freezing mixture, the vapor is cond fresh quan- 
tities rise with rapidity from the water in the other bulb, 
to be in their turn condensed; a continual condensation, 
therefore, goes on ina, and a Cota evaporation in 4, 
but the vapor thus Fane in 6 must have caloric of eine. 
ticity ; it obtains it from the water from which it is rising, 
the temperature of which therefore descends until Sit 
fication takes place, 


What effect has the Gulf Stream on the climate of Europe? Explain 
the cause of it. Describe the cryophorus. What is the reason that cold 
applied to one bulb freezes water in the other? 


—s ~~ 


HYGROMETERS. 51 


Leslie’s process for freezing water in vacuo by its own ~ 
evaporation is an example of the same kind. If some 
water in a watch-glass is placed in an exhausted receiver, 
with a large surface of sulphuric acid, as fast as vapor 
rises it is condensed by the acid; arapid Fig. 36. 
evaporation of the water therefore takes 
place, the temperature falls, and congela- 
tion finally ensues. In Fg. 36 this ap- 
paratus is represented: @ is the watch- 
glass containing water, 6 a wide dish 
filled with sulphuric acid, and ¢ a low bell jar in which 
the exhaustion is made. - 

A drop of prussic acid held in the air on the tip of a rod 
solidifies, the portion that evaporates obtaining its latent 
heat from the portion left behind, and on the same prin- 
ciple liquid carbonic acid can also be solidified. 

The amount of watery vapor contained in the air is 
very variable. Many common facts prove this : the swell- 
ing of wooden furniture takes place in consequence of 
damp weather ; and the opposite effect, or its shrinking, 
occurs during dry. Several instruments have been invent- 
ed to determine what the amount is at any time; they 
are called hygrometers. In one of these, the relative damp- 
ness or dryness of the atmosphere is determined by the 
stretching or contracting of a hair, which is very sensitive 
to such changes. A general idea of such an instrument 
may be obtained by considering the metallic bar of the 
pyrometer, Ig. 15, to be replaced by a hair, the move- 
ments of which would of course be communicated to the 
index ; in another a slip of whalebone is used instead of 
the hair. There is a simple and ingenious instrument, 
the movements of which depend on these principles; it is 
represented in Avg. 37: a thin slip Fig. 31. 
of pine wood, @ a, cut across the @ | a 
erain, a foot long and an inch wide, UO 
has inserted into its corners four 
needles, all pointing in one direction backward ; if this 
instrument be set upon a floor or flat table, in the course 
of time it will crawl a considerable distance. During dry 


Describe Leslie’s process for freezing water in vacuo? Why does a 
drop of prussic acid held in the air solidify? How can it be proved that 
the amount of moisture in the air is variable? What is the hygrometer? 
Describe the hair hygrometer. Describe the instrument, Fg. 37. 


52 THE DEW POINT. 


weather the thin board contracts, and the two fore legs 
taking hold of the table, the hind ones are drawn up a 
little ¢ space; when the weather turns damp, the board ex- 
pands, and now the hind legs pressing against the table, 
cause the fore ones to advance. Every change from dry 
to damp, or the reverse, produces a walking motion in a 
continuous direction, and the distance passed over is a 
register of the sum total of these changes. 

But of all these hygrometric methods, the process 
known as ‘the determination of the dew point” is by far 
the most philosophical. This method consists in cooling 
the air until it begins to deposit moisture. When there is 
much moisture in the air, it obviously requires but a slight 
diminution of temperature to cause a portion of the vapor 
to deposit as a dew; but when the air is dryer, the cool- 
ing must be carried to a greater extent. The precise 
thermometric point at which the moisture begins to de- 
posit is called the dew point. 

Thus, if we take a thin metallic vessel containing water, 
and cool it gradually by the addition of a mixture of 
nitrate of potash and sal ammoniac, or any of the cooling 
mixtures, continually stirring with the bulb of a small 
thermometer, as soon as the temperature has reached a 

Fig. 38. certain point a dew is 
= - deposited on the outside 
of the metallic vessel ; 
that temperature is the 
dew point for the time 
being. Knowing the tem- 
perature of the air, the 
dew point, and the baro- 
‘metric pressure, the abso- 
lute amount of vapor can 
be determined by a sim- 
\, ple calculation. 
Daniell’s hygrometer 
Y affords a ready and beau- 
tiful method of determin- 
ing the dew point. It 
consists of a cryophorus, 


ac b, Fig. 38, the bulb 


What is meant by the “dew point?” What is the process for ascer- 
taining it? Describe Daniell’s hygrometer and the mode of using it. 


as 


SPECIFIC GRAVITY OF VAPORS. 53 


6 being made of black glass, and @ covered over with 
muslin. The bulb 6 contains ether instead of water, and 
into it there dips a very delicate thermometer, d. Usually, 
another thermometer is aflixed to the stand of the instru- 
ment. When a little ether is poured on a, by its evapo- 
ration it cools that bulb, and ether distils over from 3, 
which, of course, also becomes cold. After a time, the 
temperature of 6 sinks to the dew point, and that bulb 
becomes covered with a mist. The thermometer, d, then 
shows at what temperature this takes place, and of course 
gives the dew point. 


LECTURE XIII. 


Evaporation AND InTERSTITIAL RapiaTion.— Methods 
of Gay-Lussac and Dumas for ascertaining the Specific 
Gravity of Vapors—Phenomena of Evaporation. 
Control of Temperature—Effect of Dryness, Stillness, 
Pressure, and Surface-—LEvaporation a Cooling Pro- 
cess.— Conduction of Solids— Difference among different 
Metals.—Rumford’s Experiments. 


THE specific gravity of vapors may be de- 
termined in several ways. The following is 
the method of Gay-Lussac: A’ graduated jar, 
a, is inverted in a basin of mercury, c, which 
rests upon a small furnace. A glass bulb is to 
be filled quite full with the liquid under ex- 
amination, and the quantity introduced is aecu- 
rately weighed. The bulb is now slipped into 
the jar, a, and rises to its top. A cylinder, 4, 
open at both ends, but the lower pressed down 
into the mercury, is next-placed round a, and |= 
the interval filled with clear oil. The furnace [iy 
is now lighted ; the oil and the mercury be- | ee 
come warm ; the bulb at last bursts, and, as its ~ 
vapor depresses the mercury in the graduated jar, its vol- 
ume may be determined. Thus, knowing the weight of 
. the liquid, the volume of its vapor, and the temperature 


Describe Gay-Lussac’s method of determining the aRRCIES gravity of a 
vapor. 
E 2 


54 SPECIFIC GRAVITY OF VAPORS. 


of the oil, we can easily calculate the volume at 32°, and 
from that deduce the specific gravity. 
The method of Dumas consists in weighing a glass globe 


Fig. 40. filled with the 
vapor to be 
tried. <A por- 


tion of the sub- 
stance is to be 
introduced in- 
to the globe, 
the weight of 
which is jirst 
determined, 
and this is then 
held, as shown 
in the figure, in 
a bath of fusi- 
ble metal pla- 
ced over a small furnace. The heat of the melted metal 
vaporizes the substance, drives out the air, and occupies 
the whole cavity in a state of purity. When no more 
vapor escapes from the end of the tube it is sealed by the 
blow-pipe, and the temperature of the bath ascertained. 
The globe is now to be carefully weighed, when cold, a 
second time, and the point of the tube is then broken un- 
der quicksilver, which rises and fills it completely, and 
this being subsequently emptied into a graduated jar, the 
volume of the globe is ascertained. Knowing the vol- 
ume of the globe, we know the weight of the air it con- 
tains, and this, subtracted from the first weight, is the 
weight of the glass when empty. Subtracting this again 
from the second weighing, gives us the weight of the va- 
por, and as the air and the vapor occupied the same vol- 
ume, their densities are as their weights. But, as their 
temperature was different, a farther calculation is required 
to bring them to the same standard. 

There are several conditions which exert a control 
over the rapidity of evaporation. The amount of vapor 
which can exist in a given space depends entirely on the 
temperature. ‘Thus the air included in a glass jar which 
is standing over water contains, at 32°, a certain quantity 


Describe the method of Dumas. What is it that regulates the quantity 
of vapor in a given-space ? 


CAUSES CONTROLLING EVAPORATION. 55 


of vapor; but if the temperature rises to 60°, it contains 
more, and still more if it rises to 90°. Should the tem- 
perature descend, a part of the vapor is deposited as a 
mist. The quantity that remains in suspension is determ- 
ined by the temperature alone. 

It is the application of this principle which constitutes 
the most beautiful part of Watts’s great invention, the 
low-pressure steam-engine. Taking advantage of the 
fact that the quantity of vapor which can exist in a given 
space is determined by the lowness of temperature of any 
portion of it, he arranged a vessel, maintained uniformly 
at a low temperature, in connection with the cylinder of 
the engine, and thus reached the apparently paradoxical 
result of condensing the steam without cooling the cyl- 
inder. 

Among other causes exerting a control over evapora- 
tion in the air is the dry or damp state of that medium. 
As is well known, evaporation goes on with rapidity when 
the weather is dry, and is greatly retarded when the 
weather is damp. So, too, a movement or current exerts 
a great effect. When the wind is blowing, water will 
evaporate much more quickly than when the air is quite 
calm; this obviously depends on a constant renewal of 
surfaces, so that as fast as one portion of air becomes 
moist it is removed, and a dryer portion takes its place. 
Extent of surface operates in the same way; the same 
quantity of water will evaporate much more rapidly if 
exposed in a plate than if exposed in a cup. Pressure 
also exerts a great control; for, as we have seen, evap- 
oration takes place instantaneously in a vacuum. 

While, therefore, there are several circumstances which 
can control the rate of evaporation, it is temperature alone 
which regulates the absolute and final amount. As we 
have just seen, a fixed quantity of vapor can exist in a 
certain space at a given temperature; and it matters not 
whether that space is full of atmospheric air or is a vacu- 
um, the absolute quantity will be precisely the same. 

At one time it was supposed that evaporation was due 
to a solvent power in the air—a kind of attraction be- 
tween that medium and the water with which it is in con- 


On what principle does the steam-engine condenser depend? What 
effect have dryness or dampness over evaporation? What is the effect 
of a current? What of extent of surface? What of pressure? What 

of temperature ? 


56 EVAPORATION IS A COOLING PROCESS. 


tact; but it is clear that such an opinion is wholly untena 
ble, for the process goes forward with the greatest rapid- 
ity in a vacuum, when the air is totally removed. 

Although the evaporation of liquids, such as water, wilt 
take place at very low temperatures, there is reason to be- 
lieve that the process has a limit; thus,a minute quantity 
of vapor will rise from quicksilver at a temperature of 
60°, but at 40° not a trace can be discovered. 

All processes of evaporation are cooling pr ocesses, be- 
cause the vapor developed requires latent heat to give it 
the elastic form. For this reason, when any vaporizable 
liquid, as ether, is poured on the bulb of an air thermom- 
eter, or on the hand, cold is produced. 

Fig. 41. The pulse glass is an instru- 


oN ment which may serve as an 
SS 
SS” 


illustration: it consists of a 
glass tube, bent twice at right 
angles, and terminated by 
bulbs, as in Fie. 41. It is partially filled with spirit of 
wine, the rest being occupied by the vapor of that sub- 
stance. On grasping one of the bulbs in the hand, the 
warmth is sufficient to boil the liquid ; and as it distills 
over into the other bulb, an impression of cold is felt. 

We now come to the consideration of the mode by 
which heat is transmitted through bodies, or interstitial 
radiation, called by many writers conduction ; a term in- 
volving the idea that the particles of bodies are in actual 
contact, whereas it has been abundantly proved that they 
are separated from each other by interstices. The pass- 
age of the heat across these spaces is what is meant by in- 
terstitial radiation. From the currency which it has ob- 
tained, and the convenience of the expression, I shall con- 
tinue to use the word conduction. 

Different solids conduct heat with different degrees of 
facility. If we take a cylindrical mass of metal, and hold 
tightly against its surface a piece of white writing paper, 
the paper may be placed in the flame of a spirit lamp for 
a considerable time without scorching; but if we take a 
cylindrical piece of wood of the same dimensions, and, 


Does evaporation arise from a solvent power in the air? Is there any 
limit to evaporation? Why are processes of evaporation cooling _pro- 
cesses? Describethe pulse glass. What is interstitial radiation? ‘What 
is conduction? How may it be proved that wood and metals conduct 


with different degrees of facility ? 
4 


CONDUCTION OF HEAT. 57 


wrapping the paper round it, expose it to the flame, it 
rapidly scorches. The “metal, therefore, keeps the paper 
cool by carrying off its heat, but the wood, being a bad 
conductor, suffers the paper to burn. 

By the aid of the apparatus of Ingenhouse, Ag. 42, the 
same fact may be proved in a more gen- Fig. 42. 
eral way. It consists of a trough of brass, 
six inches or more long, three wide, and 
three deep; from the front of it project 
cylinders of metallic and other substances 
of the same length and character; they 
may be of silver, copper, brass, iron, ‘porcelain, wood, &c., 
im succession ; ine surface of Sach cylinder is sineated 
with bees’ wax. On pouring boiling water into the trough, 
the heat passes along these cylinders with a rapidity cor- 
responding to their conducting power, and the wax cor- 
respondingly melts. On the silver bar the wax melts 
most rapidly, and on the wood most slowly: on the others 
intermediately ; thus affording a clear proof that different 
solids conduct heat with different degrees of facility. 

Even among metallic substances, great differences in 
this respect exist, as may be strikingly Fig. 43. 
shown by the instrument, Hig. 43. Into 
a solid ball of copper, arthreé wires of 
equal length and equal diameter are 
screwed—they may be copper, brass, and 
iron, respectively : they are flattened at 
their farther extremities, 5, c, d, so as to af- 
ford a place on which pieces of phospho- 
rus may be put. A lighted spirit lamp is 
now set beneath the central ball, the temperature of which 
soon rises, and the heat passes with different degrees of 
speed along the metals; very soon the piece of phosphorus 
at the end of the copper takes fire; then, some time after, 
follows that on the brass; and last, that on the iron; en- 
abling us to prove to persons at a distance the fact that 
these different metals conduct heat with different degrees 
of facility. 

Ifa piece of wire gauze be held over the flame of a candle 
or gas jet, Ig. 44, the flame fails to pass through; but the 


Describe the apparatus of Ingenhouse? What does it prove? Are 
there differences in the conducting powers of metals? How may that be 
proved? ; 


58 CONDUCTING POWER OF METALS. 


gaseous matter of which the flame consists 
freely escapes through the meshes of the 
gauze, for it may be set on fire, as shown in 
the figure. [lame is gaseous matter, or 
solid matter in a state of excessive sub- 
division, temporarily suspended in gas, 
brought to a very high temperature. It 
can not, therefore, pass through a piece of 
wire gauze, because the metallic threads, 
exerting a high conducting power, ab- 
stract its heat “from the ficaideacent gas, 

and bring its temperature down to a point at which it ceas- 
es to be Rea The safety- -lamp of Davy is an appli 

cation of this principle; by it Be rere is prevent- 
ed from spreading through masses of explo- 
sive gas, by calling into action the conduct- 
ing power of a metallic gauze, with which the 
lamp flame is surrounded, as in fig. 45. The 
safety-tube of Hemmings, used to prevent ex- 
plosions in the oxyhydrogen blow-pipe, acts on 
the same principle. 

Count Rumford made several experiments to 
determine the conducting power of those vari- 
ous materials which are uséd for the purpose of 
clothing. He placed the bulb of a thermometer 
in the center of a spherical glass globe of lar- 
ger diameter, and filled the interspace with the 
substances to be tried. Having immersed the 
apparatus in boiling water until it was at 212°, 
he transferred it to melting snow, and ascertain- 
ed how long it took to fall a given number of degrees. 
Linen and cotton were found to be better conductors 
than wool and the various furs, and hence the reason that 
they are preferred as articles of summer clothing; but 
he also found that much depended on the tightness 
with which the substances were packed, for the ae 
ing power apparently rose when they were closely com- 
pressed. These bodies act, therefore, as will hereafter 


Can the flame of a candle pass through a piece of wire gauze? What 
is the reason of this? What is the construction and principle of ._Davy’s 
safety-lamp ? On what method did Rumford proceed to determine the 
conducting power of clothing? What was the effect of compression? 
How are these results connected with the non- conducting power of air? 


~ 


CONDUCTION OF LIQUIDS. 59 


be more distinctly seen, not so much by their own badly- 
conducting power, as by calling into action the non-con- 
ducting quality of atmospheric air. 


LECTURE XIV. 


Conpvction.—Oonduction of Liquids—Transference of 
Heat by Circulation — Conduction of Gases.—Conduct- 
ing Power of Clothing. 


Tue conducting power of most liquids, such Fig. 46. 
as water, is very low; a thin stratum is sufficient MN 
almost entirely to cut off the passage of heat. (( \ | 
This may be shown by an apparatus such as Ig. & 

46, consisting of a jar, a, nearly filléd with water, | \ 
with an air thermometer included in such a man- =] 

ner that the bulb, J, is within a short distance of 
the surface, a depth of a quarter of an inch or 
less intervening. The tube of the thermometer 
may be passed through the lower mouth of the 
jar, c, water-tight by means of a cork, and the position - 
at which the index-liquid stands having been-marked, 
some ether is poured on the surface of the water, upon 
which it readily floats, and then set on fire. A very volu- 
minous flame is the result, and a great deal of heat is 
evolved; and, since the bulb of the thermometer is appa- 
rently separated from the burning ether by a thin film of 
water only, if the heat traversed that film the thermome- 
ter should rapidly move; but the experiment proves it 
does not; and we therefore conclude that water is a 
very bad conductor of caloric. 

While this conclusion is true, a little consideration will 
show that this experiment presents the facts in a very de- 
ceptive way; and though, from its imposing character, it 
is generally relied on as a complete proof, yet were wa- 
ter a much better conductor than what it actually is, the 
same results would be obtained. All flames, as we shall 
hereafter see, are hollow; they are merely incandescent 
on the surface. A great distance, in reality, intervenes be- 


How does the conducting power of liquids compare with that of solids ? 
How may water be proved to be a bad conductor? What deceptive cir- 
cumstances are there in this experiment ? 


60 CURRENT ACTION IN WATER. 


tween the thermometer bulb and the points of high tem- 
perature, and in addition, the ether is rapidly evaporating 
away to feed the flame, and all evaporations are cooling 
processes. 

To a certain extent, all liquids conduct heat: thus, mer- 
cury is a very good conductor; but in those liquids of 
which water is the type the dissemination of heat is chief- 
ly determined by the mobility of their particles, a process 
which passes under the name of convection or circulation. 

Fig. 47. The apparatus, Fig. 47, illustrates the na- 

ture of this process; it consists of a wide 
qd tube into which water may be poured; the 
}————> lower portion, as high as a, being colored 
— blue by the addition of some coloring sub. 
stance, the intermediate por tion, from a to 3B, 
being colorless, and the upper portion, from 
6 to c, being tinged yellow. Now, by the 
application of a tea? hot iron ring, d, of such 
a diameter that it can sutround the jar, a 
space of an inch or more intervening all 
round, the upper, yellow portion may be 
made even to boil: it shows no disposition 
to intermix with the portions beneath. But if the red- 
hot ring is lowered down so as to surround the blue por- 
tion, as it becomes warm it will be found to ascend, first 
through the colorless stratum, and finally through that 
tinged yellow, on the top. When the lower portion of a 
liquid is warmed, currents are established, which, rising 
through the strata above, bring about a rapid dissemina- 
tion of the heat. 

Fig. 48. This may also be shown by taking a jar, Fig. 

A8, a, and filling it with water, ‘rendered a, 
little more dense’ by some sulphate of soda, so 
as to bring its specific gravity near that of some 
pieces of amber thrown into it. Ifa lamp now 
be applied to the bottom of the jar, currents 
are established in the water, rising up the cen- 
ter and descending down the sides of the li- 
quid ; and in this manner, new portions con- 
stantly presenting themselves on the surface 


Do liquids conduct heat at all? What are the relations of mercury in 
this respect? By what process does the dissemination of heat in a liquid 
take place? Describe the experiment represented in Fug. 47. Describe 
that represented by Fig. 48. 


PROPAGATION OF HEAT IN LIQUIDS. 61 


exposed to the flame, the whole mass becomes uniformly 
hot. 

The cause of this movement is due to the fact that 
when water is heated it expands. Those portions, there- 
fore, which rest on the bottom of the vessel, and to which 
the heat is applied, as soon as they become warm, dilate, 
and, being lighter than before, rise to the top of the liquid, 
while colder, and therefore heavier ones, occupy their 

lace. 

If we take a jar of water, Fug. 49, and hav- Fig. 49 
ing introduced through apertures near the top 
and the bottom the thermometers a 6, and into 
a brass trough, c, which surrounds the middle 
of the jar water-tight, pour boiling water, after 
a little time has elapsed we shall find that the 
upper thermometer has risen, but the lower 
one remains perfectly stationary. ‘The cause 
is, that through all those portions which are above the place 
at which the heat is applied, that is, the middle of the ves- 
sel, currents are made to circulate, but in all those be- 
neath no currents are established. 

When, therefore, heat is applied to the surface of wa- 
ter, it is not propagated downward; when it is applied to 
the middle of a vessel containing that liquid, all the por- 
tions above become hot, but all those below remain cold; 
and when it is applied to the bottom of the vessel, the 
whole mass soon becomes uniformly warm. 

In the vegetable world, advantage is taken of the non- 
conducting power of water in avery beautiful way. Soon 
after sunset, the leaves and other delicate parts of plants 
become covered with little drops of dew, which invest 
them on all sides. Under these circumstances the pro- 
cess of convection, or the establishment of currents, is en- 
tirely cut off, for each of the drops is isolated, or has no 
communication with those around. The cold air does not 
so suddenly affect these delicate organs as it would do 
were not this thin non-conducting film spread over them; 
their action is, therefore, less lable to be deranged. 

Recent accurate experiments show that all liquids con- 


W hat is the true cause of these circulatory movements ? How can it be 
proved that the warm water floats on the surface of that which is cold ? 
What is the effect of applying heat to the top, to the middle, and to the 
bottom of a vessel containing water? What advantage is taken in the 
vegetable world of the non-conducting power of water ? 


62 PROPAGATION OF HEAT IN GASES. , 


duct to a certain extent, though in many instances to a far 
less extent than what we see in the case of solid bodies. 
Among different liquids, difference in conducting power 
has also been discovered. 

If the conducting power of liquids is small, that of gas- 
eous bodies is still less perceptible. In these, as in li- 
quids, the mobility of the particles is so great that heat is 

Fig.50. readily diffused through them. ‘Thus, if we 

take a jar, Lg. 50, containing oxygen gas, 
and place a piece ae burning sulphur i in it on 
a stand, a, the vapor which rises from the sul- 
phur moves in a current to the top of the jar, 
and then descends in beautiful wreaths of 
smoke down the sides, precisely representing 
the circulatory movements of liquids. 

The ventilation of buildings and mines, and 
the proper construction of furnaces and chimneys, depend 
upon these principles. 

By taking advantage of the non-conducting power of 
air, rooms may be kept warm with a small consumption 
of en by furnishing them with double windows. A 
stratum of air, two or three inches thick, intervening 
between the windows effectually cuts off the passage of 
heat. It is upon the same principle we explain Count 
Rumford’s experiments in relation to the conducting 
power of clothing; he found that when the same fibres 
are used, the apparent facility with which they transmit 
heat depends on the closeness with which they are pack- 
ed: the non-conducting power of air is here evidently 
called into play, and the fibres act by preventing the 
production of currents. In the case of sheep, or other 
animals, which, during the winter season, are covered 
with a thick coat of wool, or fur, it is the non-conducting 
power of the included air sate is again brought into 
operation. 


Do all liquids conduct heat? Are there differences in their conducting 
power? By what process is heat diffused through gases? What is the 
use of double windows ? What connection has the non-conducting power 
of air with Count Rumford’s experiments? In the economy of animals, 
what advantage is taken of these principles ? 


NATURE OF RADIANT HEAT. 63 


LECTURE XV. 


Rapiation.—Preliminary Ideas on Radiant Heat.—Anal- 
ogies with Light—LEffect of Surfaces—Relations be- 
tween Radiation and Reflection—The Florentine Ex- 
periment.— The Cold-ray Experiment.— Opacity of 
Glass to Heat.—Jts increasing Transparency as the 
Temperature rises—Properties of Rock Salt. 


Bur, though gases are bad conductors of heat, they 
freely allow of its transmission by general radiation. A 
person who stands at one side of a fire receives the heat 
of it, although no currents of warm air can reach him. In 
a vacuum, a piece of red-hot metal rapidly cools. 

The heat which, under these circumstances, escapes 
from bodies is entirely invisible to the eye; it moves in 
straight lines, exhibiting many of the phenomena of the 
rays of licht. Thus, if we interpose between a fire and a 
thermometer an opaque screen, the moment the rays of 
light are stopped the heat is simultaneously intercepted. 

The rays of heat, like the rays of light, are capable of 
being reflected by polished metallic surfaces. If a piece 
of planished tin be held before a fire in such a position as 
to reflect the light of it upon the face, the heat, also, is 
similarly reflected, and gives rise to a sensation of warmth. 

The analogy between light and heat is farther observed 
when rays of the latter fall upon bodies of a different 
physical constitution from the metals. As glass is trans- 
parent to light, there are many bodies transparent to rays 
of heat, though, as we are presently to find, these bodies 
are not the same in both instances. And as there are 
substances, like lamp-black, which will absorb all the light 
which impinges on them, there are many which perfectly 
absorb heat: reflection, transmission, and absorption are 
therefore common to both these agents. 

If we take two metallic vessels of the same size and 
shape, and having blackened one of them all over with 


Do gases transmit radiant heat? How may it be proved that radiant 
heat moves in straight lines? Is it capable of reflection? Are there any 
substances transparent to radiant heat? Are these the same bodies that 
are transparent to light? 


64 VARIATION OF SURFACE RADIATION. 


the smoke of a candle, fill them both with hot water, and 
notice their rate of cooling, it will be seen that the black- 
ened one cools faster ; hes same thing may be observed, if, 
instead of blackening ‘the vessel, it is Covered with layers os 
varnish. ‘These results may be proved by the aid of Les- 
lie’s canister, which consists of a cubical brass vessel, a, 

Fig. 51. Mg. 51, set upon a verti- 
cal stem, upon which it 
can rotate; at a little dis- 
tance is placed the black- 
ened bulb of a differential 
thermometer, d ; a mirror, 
M, receives the rays of 
the canister and reflects 
them on the thermometer. 
One of the vertical sides of the cube is left with a clear 
metallic surface, a second washed over with one coat of 
varnish, the third with two, and the fourth with three 
coats; if these sides be presented in succession to the 
thermometer, they will be found to radiate heat with 
very different degrees of speed, more heat escaping from 
them as the number of coats is increased. In the exper- 
iments of Melloni, it was found that the maximum was 
not attained until sixteen coats were applied. 

These results can only be explained on the principle 
that radiation does not take place from the surface of 
bodies merely, but from a certain depth in their interior. 

A highly-polished metal is a bad radiator, but on rough- 
ening the surface, its quality is improved. As a general 
rule, good radiators are bad reflectors, and good reflectors 
are bad radiators. 

When rays of light, diverging from the focus of a con- 
cave parabolic mirror, impinge on the surface, they are re- 
flected in parallel lines; when parallel rays fall on such 
a surface, they are reflected to its focus. Thus, if from 
the point a, Fug. 52, the focus of a parabolic concave, c 
J, rays diverge, they will be reflected in parallel lines, ¢ g, 


Of two surfaces, one polished and the other blackened, which radiates 
heat best? When successive layers of varnish are put on a surface, what 
is their effect? -When is the maximum reached? What is the explana- 
tion of these results? What is the general connection between radiation 
and reflection? When rays diverge from the focus.of a concave mirror, 
what is their path after reflection 1 ? When parallel rays fall on a concave 
mirror, what is their path after reflection ? 


EXPERIMENT WITH CONJUGATE MIRRORS. 65 


dh,ei, fk, and if at these points they be intercepted by 
the mirror, g /, they will be reflected to its focus, . 

Now, as the laws of reflection of radiant heat are the 
same as the laws of the reflection of light, it is plain that 
if we place any incandescent body, Roan as a red-hot 
cannon-ball, in the focus, a, the heat which radiates from 
it will finally be found at the other focus, b. 

Fig. 52. 


This is beautifully illustrated by an experiment known 
under the name of the experiment with conjugate mir-_ 
rors. In the focus, a, Fig. 52, of a parabolic mirror,’¢ f, 
place a red-hot cannon-ball, and in the focus, 4, of a 
second mirror, g k, set opposite, but twenty or thirty 
feet off, place a piece of phosphorus, a screen intervening 
between. As soon as the arrangements are completed, 
remove the screen, and in a moment the phosphorus takes 
fire. That this effect is due to the reflecting action of the 
mirrors, as has been described, may be proved by re- 
moving the mirror, c f, when it will be found that the 
phosphorus can not be lighted, even though the ball be 
brought within a very short dineutee of it. 

This striking experiment proves, first, that the rays of 
heat move in straight lines, like those af light; and, sec- 
ond, that in the same manner they are subject ‘és the ordi- 
nary laws of reflection. 

A variation of the foregoing experiment may be made 


When a hot ball is placed in the focus of one of the mirrors, to what 
point does its heat converge? Describe the Florentine experiment rep- 
resented in /ig.52. What two facts does this experiment prove ? 


FP 2 


66 OPACITY OF GLASS TO HEAT. 


by using a snowball instead of the cannon-shot, in which 
case a thermometer placed in the focus of the opposite 
mirror will exhibit a reduction of temperature. From 
this it was at one time supposed that there existed rays 
of cold precisely analagous to rays of heat, and that they 
observed the same law as respects the rectilinear nature 
of their movement, and were also subject to the law of re- 
flection ; but, as we shall see when we come to speak of 
the Theory of the Exchanges of Heat, a simple explana- 
tion of the whole result can be given, without implying 
the existence of a principle of cold analogous to the prin- 
ciple of heat. 

Let it be now supposed that in the focus of the mirror, 
gk, Fig. 52, the bulb of a delicate thermometer is placed, 
and in the focus of the other mirror, cf, a metalline mass, 
a, the temperature of which we can vary at pleasure. 
Between the mirrors let there be interposed a screen of 
transparent plate glass; and let us farther suppose that 
the temperature of a is 212°, or considerably below the 
point at which it is visibly red hot. Under these circum- 
stances the thermometer exhibits no rise of temperature 
so long as the glass intervenes, but the moment it is re- 
moved the heat passes. 

A piece of transparent glass is, therefore, opaque to 
the rays of heat which come from a non- oningue source. 

Let us now suppose that the temperature of the metal- 
line mass, @, continually rises. When it has reached a 
red heat, a certain proportion of the rays emitted by it 
begins to pass through the glass, as is shown by their 
effect upon the thermometer. When the mass is visibly 
red hot in the daylight the rays go through the glass more 
readily, and when it has become white hot, or has reached 
the highest temperature we can give it, the glass trans- 
mits the rays with facility. 

These facts are of the utmost importance. They show 
that bodies transparent to light are not necessarily trans- 
parent to heat, and, therefore, that light and heat are 
separate and independent agents. They farther show, 
that, as respects glass, its transparency for heat differs 


— 9 
When a snowball is used instead of a hot shot, what is the result ? 
What is the relation of glass to radiant heat of low intensity ?° What 
changes take place in the transmissive power of the glass as the tem- 
perature rises? How are these facts connected with the physical inde- 
pendence of light and heat? 


RADIANT HEAT OF DIFFERENT COLORS. 67 


with the temperature of the source from which the rays 
come. ; ; 

There is a certain well-known substance, rock salt, with 
which, if we could obtain plates large enough to inter- 
vene completely between the two mirrors, a different 
series of results would be exhibited. Whatever might 
be the temperature of the source, whether low or high, 
the rays would pass it with equal freedom. The warmth 
of the hand and the rays from melting iron would go 
through it alike. This substance, therefore, is permeable 
to all kinds of heat, as glass is permeable to all kinds of 
light. It constitutes the true glass for heat. ° 

The great conclusion which we draw from the experi- 
ments just described is, that there are different varieties of 
radiant heat. Some of them can pass through glass, and 
some can not. Hereafter we shall see that the intrinsic 
differences in radiant heat are due to the same cause 
which gives different colors to light. 


LECTURE XVI. 


THeory ofr THE Excuances or Hear.— Physical Inde 
pendence of Light and Heat.— Theory of Exchanges.— 
Explanation of the Cold Ray Eaxperiment.— Wells’s 
‘Theory of the Dew.—Cold on Mountain Tops.—Con- 
duction a Form of Radiation — Temperature of the Sun. 


Tue earlier writers on chemistry supposed that if light 
and heat are not the same principle, they are mutually 
convertible; that when the rays of light fall on any ob- 
ject and warm it, they do so because they become ex 
tinguished and changed into heat. 

But there are many facts which militate against this 
doctrine. A vessel containing hot water radiates heat, 
and that heat is totally invisible in a dark room, nor can 
it be made to assume the luminous condition, even though 
concentrated by large concave mirrors. 


What are the properties of rock salt? Why is it the glass of heat? 
What general conclusion is drawn from the foregoing facts? What are 
the varieties of radiant heat due to? What relation was formerly sup- 
posed to exist between light and heat? Can rays of heat exist without 
being visible ? 


68 THEORY OF EXCHANGES OF HEAT. 


Experiments have been made to determine whether in 
the moonbeams there are any calorific rays. The most 
delicate thermometers, aided by concaye mirrors, have 
hitherto failed in detecting the minutest trace. In this in- 
stance, therefore, we have light existing without heat; in 
the former, heat existing without light. 

In addition, as we have already shown, the relation of 
transparency for these two agents is not the same. A 
piece of smoky quartz, or dark-colored mica, of such a 
degree of opacity as scarcely to admit a ray of light to 
pass, is freely traversed by radiant heat. 

The theory of the exchanges of heat, comprehending 
an explanation of a great number of the phenomena we 
ordinarily witness, depends upon the following principles : 
It assumes, 1st, that all bodies, no matter what their tem- 
perature may be, are constantly radiating heat at all times; 
2d. That the rate of radiation depends on the tempera- 
ture, increasing as the temperature rises, and diminishing 
as it declines. 

Thus the various objects around us are constantly emit- 
ting caloric: the warm bodies to the cold, and the cold 
ones tothe warm. A mass of snow and a red-hot cannon- 
ball respectively give off heat, the ball emitting it in great 
quantities, and the snow in less. And even when adja- 
cent bodies have reached the same thermometric point, 
they still continue to exchange heat with one another. 

Upon these principles, we can readily account for the 
fact that bodies of different temperatures at first, finally 
come to an equilibrium. If an ignited cannon-shot be 
placed in the middle of a large room, it radiates its heat 
to the roof, the walls, the floor, and the various objects 
around : they also radiate back again upon it ; but, from its 
elevated temperature, it emits its heat faster than they, and 
therefore gives out more than it receives. Its tempera- 
ture constantly descends, and continues to do so until it 
receives just as much as it gives, which takes place when 
it has reached the same degree as the objects around; 
for, other things being equal, bodies at the same temper- 
ature radiate with equal speed. 

Can light exist unaccompanied by heat? What other evidence have 
we of the physical independence of these agents? On what does the 
theory of the exchanges of heat depend? Do bodies at the same tem- 


ae still radiate? Describe the process of cooling of an incandescent 
ody. 


THE COLD-RAY EXPERIMENT. 69 


The process must, however, stop as soon as that equal- 
ity of temperature is attained ; for, if we suppose the shot 
to cool below that point, it would evidently begin to re- 
ceive more heat from the objects around than it gave forth, 
and the excess accumulating in it, its Caray saeieae would 
at once rise. 

When an equilibrium is obtained the process of radia- 
tion still continues, but the exchanges are equal. ‘Two 
lighted candles placed together do not extinguish each 
other, or cease to exchange light with each other, nor do 
two bodies equally warm cease, for that reason, to exchange 
heat. In a room, therefore, in which every thing has the 
same temperature, rays are eternally exchanging, but each 
object maintains its own temperature, because it receives 
as much as it gives. 

If a red-hot ball and a thermometer bulb are placed 
near one another, the bulb receives more heat from the 
ball than it gives to it, and its temperature therefore rises ; 
but, if a pheamornster bulb and a snowball are placed in 
presence of one another, the bulb, being the hotter body, 
gives more than it receives, and its temperature therefore 
descends. This is the explanation of the experiment with 
the conjugate mirrors. That experiment, as was obsery- 
ed, affords no proof that there are rays of cold: the ef- 
fect 1s due to the fact that a mutual exchange is going 
forward between the two bodies, and the temperature of 
the hotter descends. The mirrors, of course, take no 
part in this phenomenon; their office is merely to direct 
the path of the rays, as has been explained. 

On the principles of the radiation of heat is founded 
Wells’s theory of the dew. After the sun goes down of an 
evening, drops of water condense on the leaves, grass, 
stones, and other objects exposed to the air. It was once 
a question whether this dew descended in the form of a 
light shower, or ascended from the ground. There are 
also certain circumstances apparently very mysterious at- 
tending its formation: the dew rarely falls on a cloudy 
night ; it also apparently possesses a selecting power, de- 


When does the descent of temperature cease? When an equilibrium 
is obtained, what is the rate of the exchanges? Describe the action in 
the case of a red-hot ball and a thermometer bulb. Describe the action of 
a snowball and a thermometer bulb. How is this connected with the ex- 
parnout with conjugate mirrors? Under what circumstances does dew 
form 7 


70 THEORY OF THE DEW. 


positing itself on some bodies in preference to others. 
The theory of Dr. Wells furnishes a beautiful explanation 
of these curious facts. During the day, the various bod- 
les on the surface of the earth, receiving the rays of the 
sun, become warm; but at nightfall, when the sky is un- 
clouded, they begin to cool; for, the process of radiation 
continuing without any source of supply, their tempera- 
ture must descend. While the sun shone, they received 
as much heat from him as they gave forth to the sky, but 
when he sets, the supply is cut off, and they therefore 
cool; and as there is always moisture in the air, their 
temper ature descending, by-and-by the dew point is reach- 
ed; they become cold ‘enough to condense water from the 
surrounding air, and this is the dew. And as different 
bodies, according to the roughness or physical condition 
of their surfaces, radiate with different degrees of speed, 
as Leslie’s canister proves, some of the objects exposed 
to the sky cool rapidly, and are covered with dew; but 
with others the dew point is never reached: hence the 
apparent selecting power. When there is a canopy of 
clouds over the sky, dew can not form, for the cloud ra- 
diates to the earth as much as the earth radiates to it: the 
exchanges are equal, and the equilibrium is maintained ; 
but if the cloud disappears, the heat of the surface of the 
ground escapes away into the regions of space, and is 
lost; hence cloudy nights are warm, and a clear is often 
a frosty night. 

For similar reasons, mountain tops are always colder 
than valleys. Ina valley, the radiation is obstructed by 
the sides of the adjacent hills, but on the top of a mount- 
ain the free exposure to the sky permits of unchecked 
radiation. ; 

It has already been observed, tnat conduction is only a 
form of radiation. In its ordinary acceptation, the term 
conduction implies passage from particle to particle, by 
reason of their being in contact; but we have proved that 
the constitution of matter involves the existence of inter- 
stices, and that heat-can only pass from among these by 


radiating across the interstices ; hence the term interstitial 


radiation. 


What is the theory of Wells? How does this explain the selecting 
power of bodies? How does it explain the action of clouds? Why is it 
colder on mountains than in valleys? What is meant by interstitial ra- 
diation ? 


a xo 


NATURE OF LIGHT. 7! 


An interesting conclusion may be drawn from the con- 
ditions of the passage of radiant heat through glass. We 
have seen it is necessary that the heat should come from 
a source of very high temperature to pass this medium 
with facility. Now the heat of the sun passes with the 
greatest freedom, as is well known when we stand before 
a window through which the sun shines. -In the focus of 
a convex lens of glass exposed in the sun’s rays, bodies 
may be readily set on fire. We infer, therefore, that the 
temperature of the sun is very high; a result which is 
corroborated by proofs drawn from other sciences. 


LECTURE XVII. 


Nature or Lient.—Vibratory Movement the Cause of 
Light.—Evolution of Light by Rise of Temperature.— 
Case of Gases.— Nature of Flame.—Artificial Lights 
of various Colors—General Properties of Light—The 
Prism.— Decomposition of Light by wt.— Nature of 
White Light-—Newton’s Theory of different Refrangi- 
bility. : | 
Tue phenomena of radiant heat lead us by impercep- 

tible steps to the phenomena of light. In treating of the 

former, we have in many cases drawn illustrations from 
the latter; and, indeed, there are facts in relation to ca- 
loric which it is absolutely impossible to understand until 
we comprehend the analogous facts im light. Such, for 
instance, is the theory which I have designated ‘“ The 

Theory of Ideal Coloration,’ and which by the most em- 

inent writers is regarded as involving the fundamental 

facts of the science of radiant heat. 

Light is the result of an undulatory or wave-like mo- 
tion, propagated through the ethereal medium, which per- 
vades all space. ‘These waves, impinging on the retina, 
an expansion of the optic nerve, situated on the posterior 
inner surface of the eye, produce in its delicate substance 
a specific chemical change. There is no difficulty in ad- 
mitting that from these changes impressed upon that sen- 


W hat conclusion may be drawn as respects the temperature of the sun, 
from the phenomena of radiant heat? What is the cause of light? How 
is the influence of light on the retina transmitted to the brain ? 


72 TRANSMISSION OF VIBRATIONS. 


sitive surface, a vibratory movement is transmitted along 
the optic nerve to the brain; for, as we shall see when we 
reach the description of a simple voltaic circuit, the oxy- 
dation of a piece of zinc may raise the temperature of a 
platina thread to a red heat hundreds of miles off, the 
movement being transmitted through a solid copper wire. 
How much more, then, might we expect to find similar 
movements communicated through a delicate nervous 
column, specially organized for Nee passage ? 

Nor is there any difficulty in admitting that through 
such a channel an infinity of vibrations may simultaneously 
pass, undisturbed by each other. All the varied objects 
around us, whatever may be their shape or whatever their 
color, simultaneously transmit through the optic nerve 
their proper impressions, which are registered in the brain. 
There are similar phenomena in the case of sound; thus, 
if we take a musical snuff box, and, removing its case, hold 
it in the air, the sound is so enfeebled that it is scarcely 

Fig. 53. audible a few feet off; but now, if the 
instrument be placed in the position d, 
Fig. 53, resting on a block of wood, 
c, which is brought fairly in contact at 
its lower end with the table, ad, the 
table begins to resound, and the musi- 
cal notes are all loudly and distinctly 
heard. But these vibrations, into which 
the table is thrown, have all passed 
through the mass of wood, c; if we touch it, it trembles 
beneath the finger. And now, no matter how shapeless 
that intervening mass may be, nor how intricate the notes 
which the instrument is executing, there is no confusion 
nor intermingling; the mass of wood and the table on 
which it rests vibrate in unison with the musical mech- 
anism. 

When the temperature of solid substances is raised to 
1000° Fahrenheit, they begin to be luminous in the day- 
light, or, as it is termed, are visibly red hot. It requires 
a far higher temperature to render a gas incandescent. 


Are there any analogous phenomena illustrating the transmission of ef- 
fects through great distances? Can such vibrations pass together through 
solid bodies without disturbing one another? Give an illustration from the 
phenomena of sound. At what temperature are solids luminous? Isa 
gas or a solid more easily made incandescent ? 


ARTIFICIAL LIGHT. "73 


. 


This may be shown by holding a piece of thin platina wire 
in the current of hot air which rises from the apex of the 
flame of a lamp; the air is not visibly ignited, but the 
platina wire instantly becomes red hot, showing the great 
difference in this respect between this metal and a gas. 

Different vapors and gases evolve different quantities 
of light when ignited. The flame of burning hydrogen is 
scarcely visible in the daylight ; that of alcohol is but little 
brighter, but, under the same circumstances, sulphuric 
ether emits much light. If we take a glass of the form 
Fug. 54, consisting of a bulb, a, and. Fig. 54. 
curved tube, 4, and having filled the 
bulb with ether, cause it to boil by 
the application of a lamp, c¢, the 
ether may be set on fire as itis forced 
out of the vessel by the pressure of 
its vapor. It burns in a beautiful 
arch of great brilliancy; but if we 
substitute alcohol for ether, the light becomes quite in- 
significant. 

The light which is emitted by lamps and candles is, 
however, in reality, due to the disengagement of solid 
matter. The constituents of the gas which produces the 
flame are carbon and hydrogen chiefly ; of these, the latter 
is the more combustible, and is first burned ; fora moment, 
therefore, the carbon exists in a solid form, in a state of 
extreme subdivision, and at a high temperature, but being 
in contact with the external air, it is immediately consumed. 

Artificial lights differ in color. If alcohol be mixed 
with common salt and set on fire, the flame is of a yellow 
tint; if with boracic acid, it is green; if with nitrate of 
strontian, it is red. It is upon these principles that the 
art of pyrotechny depends. 

From whatever source light may come, it exhibits the 
same physical properties. It moves in straight lines. 
When it impinges on polished metallic surfaces, it is re- 
flected; on dark surfaces, it is absorbed ; on transparent 
surfaces, as glass, it is transmitted. In the last case, it is 


In the combustion of vapors and gases, is there any difference in the _ 
amount of light emitted? How may this be illustrated? To what cause ~ 
are we to attribute the light emitted by lamps and candles? How may 
artificial yellow, green, and red lights be made? In what course does 
light move? What is meant by the reflection, absorption, transmission, 
and refraction of light ? 

G 


74 DECOMPOSITION OF LIGHT BY A PRISM. 

- 
frequently forced into a new path, as we shall presently 
see, and then the phenomenon takes the name of refrac- 
tion, because the ray is broken from its primitive course. 

There are two different kinds of opacity, black and 
white; charcoal is a black opaque substance, earthen- 

Fig. 55. ware 18 opaque white. 

Sir Isaac Newton first succeeded in proving 
the compound nature of light by the aid of a 
very simple instrument, a glass prism. It con- 
sists of a piece of glass having three sides, 
Fig. 55, aa, and is usually mounted on a brass 
stand, 4, with a ball and socket joint, c, which 
allows us to place it in any required position. 

Let the shutters of a room be 
closed, and through an aperture in 
one of them, suitably situated, let a 
beam of the sun enter, fig.56, a. It 
pursues, of course, a straight path, 
perish, following the dotted line, ae. Now 
a let the prism interpose in the position 
“;.¢| 5c, so as to intercept completely the 
ray. ‘This goes no longer to e, but is 
bent out of its course, and moves in 


the direction d. 

T'wo striking facts are now to be remarked: first, the 
ray @ is refracted or broken from its path; and, second, 
instead of forming on the surface d, upon which it falls, a 
white spot, an elongated and beautifully-colored image 
is produced. These colors are seven in number: red, 
yellow, orange, green, blue, indigo, violet. The separation 
of these colors from one another is desiguated by the term 
Dispersion. 

Newton has shown that white light consists of these vari- 
ous-colored rays blended together ; and their separation in 
the case before us is due to the fact that the prism refracts 
them unequally, On examining the position of the colors, 
in their relation to the point e, to which they would all 
have gone had not the prism intervened, it is ascertained 
that the red is least disturbed or refracted from its origi- 


How many kinds of opacity are there? Describe the prism. State the 
effect which ensues when a ray passes through the prism. What is meant 
by refraction? What by dispersion? What is Newton’s theory of the 
constitution of light ? 


THE SOLAR SPECTRUM. 75 


nal path, and the violet most; for these reasons, we call 
the red the least refrangible ray, the violet the most refran- 
gible, and the yellow intermediately. 

That the mixture of these colored rays reproduces 
white light, may be proved by resorting to any optical 
contrivance which will reassemble them all in one point; 
that point will be perfectly white. 


LECTURE XVIII. 


CoNSTITUTION OF THE SoLtaR SeecTRUM.— Order of the 
Colors.— Order of Intensity of the Light.— Distribution 
of Heat— The Chemical Rays.— Their Distribution.— 
Constitution of the Solar Rays. 


Let v 7, Fig. 57, represent the spectrum 
which is given by a sunbeam after its passage 
through a prism, and e the point to which it Be 
would. have gone had not the prism intervened ; 
the order ay the colors commencing with that 
which is least disturbed from its path, or nearest fey, 
to e, is as follows: 


Red, Blue, 
Orange, Indigo, 
Yellow, Violet. 
Green, 


These colors gradually blend into each other, 
so that their boundaries can not be traced; and instead 
of a circular spot, which would have resulted had they 
gone forward to e, they are dilated out, so as to form an 
elongated figure with parallel sides; at the two extremi- 
ties the light fades gradually away, so that we can not trace 
its limit with precision. 

Besides this difference of color, the light differs in in- 
trinsic brilliancy in the different spaces. Thus, if we -re- 
ceive the spectrum on a piece of finely-printed paper, we 
can read the letters in each color at very different dis- 
tances. In the yellow region the light is most brilliant, 
and there we can read farthest. [rom this point the light 
declines in brilliancy to the two ends of the spectrum, its 


Which is the least, and which the most refrangible ray 7 2 Of what does 
white light consist? What is the order of refrangibility of colors? What 
is the figure of the spectrum? How may the illuminating power be de- 
termined ? 


76 DISTRIBUTION OF HEAT IN THE SPECTRUM. 


intensity in the colored spaces being in the following or- 
der : 
Yellow, Blue, 


Green, Indigo, 
Orange, Violet. 
Red, 


Sir W. Herschel discovered, while using large reflecting 
telescopes, that the calorific rays of the sun pass with dif- 
ferent degrees of facility through colored glasses, and was 
led to examine the temperature of the colored spaces of 
the solar spectrum, to see whether the intensity of the heat 
follows the intensity of the light. It was reasonable to 
suppose that the yellow space, being the brightest, would 
be also the hottest. He therefore placed delicate 
thermometers in the various colored spaces, and 
kept them in these spaces until they had risen as 
high as the ray could bring them. ‘The thermom- 
: eter v, Fig. 58, has risen the least, and in suc- 
b ei, cession, 7,6, 2, ¥,0,7; that which was immersed 
gfe in the red being the highest. 

x or It thus appears that the distribution of heat in 
. the colored spaces of the solar spectrum is not the 
: same as the distribution of light; that the yellow 

ray, though it is the most luminous, is far from 
being the hottest, and that the intensity of the heat stead- 
ily increases from the violet to the red extremity. 

But this is not all: he farther found, that if a thermom- 
eter be brought out of the red region in the position 2, be- 
yond the limits of the spectrum, and where there is no 
light whatever, it stands higher than any of the others. 
From this a most important conclusion is to be drawn, 
that the light and heat existing in the sunbeam are dis- 
tinct and independent agents, and that by such processes 
as we are considering they may be perfectly separated 
from each other. : 

It was discovered by some of the alchemists, centuries 
ago, that the chloride of silver, a substance of snowy white- 
ness, turns black on exposure to the light. More recent- 
ly,a great number of such bodies have been found—bod- 


Fig. 58. 
Vv 


What is the order of illuminating power? Describe the discovery of 
Sir W. Herschel. Is the distribution of heat in the spectrum the same as 
the distribution of light? What fact indicates that the light and heat are 
separate and independent agents? What changes does chloride of silver 
undergo in the sunshine ? 


RAYS OF CHEMICAL ACTION. vi. 


ies which change, with greater or less rapidity, under the 
influence of this agent. The iodide of silver, which forms 
the basis of the process known as the Daguerreotype, is 
such; and a mixture of chlorine and hydrogen gases in 
equal volumes, though it may be kept unchanged for a 
great length of time in the dark, explodes violently on ex- 
posure tothe sunshine. Inthe same manner changes take 
place in a great variety of organic compounds ; the most 
delicate vegetable hues are soon bleached, and, indeed, a 
ray of light can scarcely fall on a surface of any kind 
without leaving traces of its action. 

If a piece of paper, spread over with chloride of silver, 
be placed in the solar spectrum, it soon begins to blacken. 
But it does not blacken with equal promptitude in each 
of the colored spaces; the effect takes place most rapidly 
among the more refrangible colors, and especially in the 
violet region. As in the case of heat, the effect extends 
far beyond the limit of the spectrum, and where the eye 
can not discover a trace of light. We are led, therefore, 
to conclude that there exists in the sunbeam an agent ca- 
pable of producing chemical effects, which exerts no action 
on a thermometer, which can not be perceived by the eye, 
and which therefore is neither heat nor light. 

By placing mixtures of chlorine and hydrogen in small 
vials, and immersing them in the colored spaces, we can 
readily determine the place of maximum action, and the 
distribution of the chemical influence throughout the 
spectrum. In this, as in the former instance, the greatest 
effect is found among the more refrangible colors, and 
from that point diminishes toward each extremity of the: 
spectrum. 

As the general result of this examination of the solar 
spectrum, we finally come to the conclusion that light, far 
from being a simple, is a very complex agent; that there 
exist in the sunbeam at least three separate principles: 
one which excites in our bodies the sensation of warmth; 
a second which, from its influence on the organs of vision, 
we recognize as light; and a third which determines the 


When a mixture of chlorine and hydrogen is exposed to the sun, what oc- 
curs? How does light change vegetable colors? Which ray darkens the 
chloride of silver most? What proof have we that another agent exists in 
the sun’s rays besides light and heat? What ray affects the mixture of 
chlorine and hydrogen most powerfully ?_ What is the general result ag 
respects the constitution of the sunbeam ? 


G 2 


78 PHOSPHOROGENIC RAYS. 


production of chemical changes. Future discovery may 
show that these are modifications of one common princi- 
ple, but in the present position of science we are obliged 
to regard them as essentially distinct. 

Besides these three principles, there are several facts 
which point out the existence of a fourth. When oyster- 
shells have been calcined with sulphur, they obtain the 
quality of shining after they have been exposed to the 
light. The brief flash of an electric spark is sufficient to 
make them glow splendidly; but, what is very singular, 
the rays, which in this instance bring about this result, 
can not pass through a piece of glass. Glass is perfectly 
opaque to them. We can not regard that as light which 
is unable to pass through glass; and on arguments of this 
character, I have shown that the phosphorogenic rays are 
entitled to be regarded as a distinct imponderable prin- 
ciple.—(Phil. Mag., Aug., 1844.) 


LECTURE XIX. 


Wave Tueory or Licut.—Fixed Lines in the Solar 
Spectrum.— Proofs of the Existence of the Ether —Light 
consists of Waves in it—The Hthereal Particles move 
but little— Distinction between Vibration and Undula- 
tion. — Fresnel’s Theory of Transverse Vibrations. — 
Transverse and Normal Waves.—Brilliancy of Light 
depends on Amplitude of Vibration. 


In the foregoing examination, we have found that light 
is very far from being asimple agent; it contains at least 
four distinct principles: heat, light, chemical action, and 
phosphorescence ; but of each of these there are many 
modifications. ‘The eye proves to us that of light there 
exist at least seven different varieties, answering to the 
seven colors, and besides this, innumerable intermediate 
tints; the same subdivision may be traced for each of the 
other principles. 

When the aperture which admits a ray of light into the 
dark room, Fug. 56, is a narrow fissure or slit, not more 


What proof is there of the existence of a fourth principle? Can the 
phosphorogenic rays of an electric spark pass through glass? Are there 
nny subsidiary modifications besides the four here mentioned ? 


he 


WAVE THEORY OF LIGHT. 79 


than the one thirtieth of an inch in width, the spec- 
trum which is formed by the action of a prism is 
crossed by great numbers of black lines. ‘These 
always are found in the same position, as respects 
the colored spaces, and, from the invariability of 
that position, are much used as boundary marks. 
They are designated by the letters of the alpha- 
bet, and their relative magnitude, with their po- 
sition, is given in Fig. 59. 

It has already been said that the cause of light 
is an undulatory movement taking place in the 
ethereal medium. That such a medium exists 
throughout all space, seems to be proved by a 
number of astronomical facts. It exerts a resist- 
ing agency on bodies moving in it. From its 
tenuity, we should scarcely expect that it would - 
impress any disturbance on the great planetary masses ; 
but on light gaseous cometary bodies it produces a per- 
ceptible action. The comet of Encke, with a period of 
about 1200 days, is accelerated in each revolution by 
about two days; and that of Biela, with.a period of 2460 
days, is accelerated by about one day. As there is no 
other obvious cause for these results, astronomers have 
very generally looked upon them as corroborative proofs 
of the existence of a resisting medium, that universal ether 
to which so many other facts point. 

In this elastic medium, undulatory movements can be 
propagated in the same manner as waves of sound in the 
air. It is to be clearly understood that the ether and light 
are distinct things; the latter is merely the effect of move- 
ments in the former. Atmospheric air is one thing, and 
the sound which traverses it another, The air is not 
made up of the notes of the gamut, nor is the ether com- 
posed of the seven colors of light. 

Across the ether, undulatory movements, resembling, in 
many respects, the waves of sound in the atmosphere, tr av- 
erse with prodigious velocity. From the eclipses of Ju- 
piter’s satellites, and other astronomical phenomena, it 
appears that the rate of the propagation of light, or the 


What are the fixed lines? How are these lines designated, and what 
is their use? What proofs have we of the existence of an ethereal me- 
dium? What is the relation between the ether and light? At what 
rate is light propagated ? 


80 MECHANISM OF WAVES. . 


velocity with which these waves advance, is 195,000 miles 
in asecond. We are not, however, to understand by this 
that the ethereal particles rush forward in a rectilinear 
course at that rate: those particles, far from advancing, 
remain stationary. 

If we take a long cord, a b, Fig. 60, and having fast- 

Fig. 60. ened it by the extrem- 
ity, 6, to a fixed obsta- 
cle, commence agita- 
ting the end, a, up and 

down, the cord will be 
thrown into wave-like motions passing rapidly from one 
end to the other. This may afford us a rude idea of the 
nature of the ethereal movements. The particles of which 
the cord is composed do not advance or retreat, though 
the undulations are rapidly passing. 

So, too, if in the center, c, of a surface of water, Fig. 
61, we make a tapping motion with the 
finger, circular waves are propagated, 
which, expanding as they go,soon reach 
the sides of the vessel which holds the 
water. A light object placed on the 
surface is not violently drifted forward 
by the waves, but remains entirely mo- 
tionless. We see, therefore, that there 
is a wide distinction between the mo- 
tion of a wave and the motions of the particles among 
which it is passmg. They retain their places, but the 
wave flows rapidly forward. 

A distinction is to be made between the words vibra- 
tion and undulation. In the case of the cord, Fig. 60, the 
vibration is represented by the movement exerted by the 
hand at the free extremity, a; the undulation is the wave- 
like motion that passes along the cord. In the case of 
the water, ve. 61, the vibration was represented by the 
tapping motion of the finger, the undulation by the result- 


ing wave. We, therefore, see that these stand in the re- - 


lation of cause and effect : the vibration is the cause, and 


the undulation the effect. ‘Throughout the ethereal medi- : 


Do the ethereal particles move forward at that rate? How may the 
movements of ethereal waves be represented by a cord? How may they 
be represented on the surface of water? Do the vibrating particles move 
forward with the wave? What is the distinction between vibrations and 
undulations ? 


THEORY OF TRANSVERSE VIBRATIONS. 81 


um, each particle vibrates and transmits the undulatory 
effect to the particles next beyond it. 

In the same way as a vibrating cord agitates the sur- 
rounding air, and makes waves of sound pass through it, 
so does an incandescent or shining particle, vibrating with 
prodigious rapidity, impress a wave-like movement on the 
ether, and the movement eventually impinging on the eye 
is what we call light. 

To refer again to the simple illustration given in Fig. 
60: it is obvious that there are an infinite variety of di- 
rections in which we may vibrate that cord or throw it 
into undulations. We may move it up and down, or 
horizontally right and left, and also im an infinite number 
of intermediate directions, every one of which is trans- 
verse, or at right an- Fig. 62. 
gles to the length of b eS 
the cord, as a a, b 4, 
Porc OC eee O2e.€ 
This is the peculiari- b 
ty of the movement @ 
of light. Its vibrations are transverse to the course of the 
ray; and in this it differs from the movement of sound, in 
which the vibrations are normal, that is to say, executed in 
the direction of the resulting wave, and not at right angles 
Prine : 

This great discovery of the transverse vibrations of 
light was made by M. Fresnel. It is the foundation of . 
the whole theory of optics, and offers a simple but brill- 
iant explanation of so many of the phenomena of light, 
that the undulatory theory is by many writers designated 
the THrory or TRANSVERSE VIBRATIONS. 

It may, however, be remarked, that though light con- 
sists of rays originating in these transverse motions, it is 
not impossible that there may be other phenomena which 
correspond to movements in other directions. To those 
movements our eyes are totally blind, and hence we can 
not speak of them as light. In the same way there may 
be motions in the air, due to transverse vibrations, but to 
them our ear is perfectly deaf. But it is not improbable 
that God has formed organs of vision and organs of hear- 


s 


How does each ethereal particle propagate the wave to those beyond 
it? Is there any analogy between sound and light? In how many ways 
may a cord be vibrated? What is implied by the term theory of traus- 
verse vibrations? Are other motions possible ? 


82 COLORS DEPEND ON WAVE-LENGTH. 


ing in the case of other animals upon a different type ; 
eyes that can perceive normal vibrations in the ether, 
and ears that can distinguish transverse sounds in the air. 

Lights differ from each other in two striking particulars 
—brilliancy and color. ‘These are determined by certain 
affections or qualities in the waves. On the surface of 
water we may have a wave not an inch in altitude, or a 
wave, as the phrase is, ‘‘ mountains high.’”’ Under these 
circumstances, waves are said to differ in amplitude; and, 
transferring this illustration to the case of light, a wave, 
the amplitude of which is great, impresses us with a sense 
of intensity or brilliancy, but a wave, the amplitude of 
which is little, is less bright. The brilliancy of light de- 
pends on the magnitude of the excursions of the vibrating 
particle. 


LECTURE XX. 


WAVE Tees or Ligutr.—Colors of Light depend upon 
Wave Lengths.— Interference of Sounds.— Young’s 
Theory of Interference of Light.—Condition of Inter- 

ference.—Explanation of Lights and Shades in Shad- 


ows. 


By the length of a wave upon water, we mean the dis- 


Fig. 63. tance that 1 inte retiae from the crest 

a 6 of one wave to that of the next, or 

from depr ession to depression. 

c d Thus, in Fig. 63, from a@ to 4, or, 


what is the same, from c to d, constitutes the wave lensth. 

In the ether the length of the waves determines the 
phenomenon of color; this may be rigorously proved, as 
we shall soon see, when we come to the methods by which 
philosophers have determined the absolute lengths of un- 
dulations. It has been found that the longer waves give 
rise to red light, the shorter ones to violet, and those of 
intermediate magnitudes the other colors in the order of 
their refrangibility. 

Two rays of light, no matter how brilliant they are sep- 


What is meant by the amplitude of waves? On what does the brillian. 
cy of light depend? What is meant by the length of a wave? mee is. 
the connection between color and wave length ? ex 

% 


TWO SOUNDS PRODUCE SILENCE. 83 


arately, may be brought under such relations to one 
another as to destroy each others effect and produce dark- 
ness. Light added to light may produce darkness. ‘Two 
sounds may bear such a Srolanain to each other that they 
shall produce silence; and two waves, on the surface of 
water, may so interfere with one another that the water 
shall retain its horizontal position. 

Take two tuning forks of the same note, and fasten by 
a little sealing wax on one prong of each a 
dise of card-board, half an inch in diameter, 
as seen Fg. 64, a. Make one of the forks a 
little heavier than the other, by putting on 
the end of it a drop of the wax. 

Then take a glass jar, b, about two inches 
in diameter and eight or ten long, and having 
made one of the forks vibrate, hold it over 
the mouth of the jar, as seen at d, its piece 
of card-board being downward ; commence pouring water 
into the jar, and the sound will be greatly re-enforced. 
It is the column of air in the jar vibrating in unison with 
the fork, and we adjust its length by pouring in the water; 
when. the sound is loudest, we cease to pour in any more 

water, the jar is adjusted, ‘and we can now prove that two 
sounds added together may produce silence. 

It matters not which fork is taken, whether it be the 
light or the loaded, on making it vibrate and holding it 
over the mouth of the resonant jar, we hear a uniform 
and clear sound, without any pause, stop, or cessation. 
But if we make both vibrate over the jar together, a re- 
markable phenomenon arises, a series of sounds alterna- 
ting with a series of silences; for a moment the sound in- 
creases, then dies away and ceases, then swells forth 
again, and again declines, and so it continues until the 
forks cease vibrating. The length of these pauses may be 
varied by putting more or less wax on the loaded fork ; 
and as we can see that even during the periods of silence 
both forks are rapidly vibrating, the experiment proves 
ig two sounds taken together may produce silence. 

eaer these circumstances, waves of sound are said to 


eant by the interference of lights or of sounds? Give an il- 
interference of sounds. “What is the character of the 
resonant jar emits? Why are there pauses in it? At 


84 LAWS OF INTERFERENCE. 


interfere with each other, and in like manner interference 
takes place among the waves of light. We can gather 
an idea of the mechanism by considering this case in waves 
upon water, in which, if two undulations encounter under 
such circumstances that the concavity of the one corre- 
sponds with the convexity of the other, they mutually de- 
stroy each other’s effect. 

If two systems of waves of the same length encounter 
each other after having come through paths of equal length, 
they will not interfere. Nor will they interfere even 
though there be a difference in the length of these paths, 
provided that difference be equal to one whole wave, or 
two, or three, &c. 

But if two systems of waves of equal length encounter 
each other after having come through paths of wnequal 
length, they will interfere, and that interference will be 
complete when the difference of the paths through which 
they have come is half a wave, or 11, 21, 31, &c. 


Fig. 65. These cases are respectively shown 

Oi gq atab,andc d, Fig. 65, at the point 
a of encounter, z ; in the first instance, 
6 the two sets of waves are in the same 

A phase, that is, their concavities and 


~ ¢ convexities respectively correspond, 
¢ Z and there is no interference; but in 
the second case, at the point of en- 


counter, 2, the two systems are in opposite phases, the 
convexity of the one corresponding with the concavity ot 
the other, and interference takes place. 
Upon these principles, we can account for the remark- 
Fig. 66. able results of the following experi- 
|} ment: From a lucid point, s, Ig. 
66, which may be formed by the 
rays of the sun converged by a dou- 
ble convex lens of short focus, or by 
passing a sunbeam through a pin- 
hole, let rays emanate, and in them 
place the opaque obstacle, a 6, which 
we will suppose to be a cylindrical 


aaa 8 


When two waves upon water encounter each other, under what cir- 
cumstances will they interfere? When systems of waves of equal length 
encounter one another, when do they, and when do they not, interfere ? 
Describe the experiment represented in J/g. 66. 


INTERFERENCE OF LIGHT. 85 


body, seen endwise in the figure; at some distance beyond 
place a screen of white paper, c d,.to receive the shadow. 
It might be supposed that this shadow should be of a 
magnitude included between x y, because the rays, s a, 
s 6, which pass the sides of the obstacle impinge 
on the paper at those points. It might farther be 
supposed, that within’the space z y the shadow 
should be uniformly dusky or dark; but, on exam- 
ining it, such will not be found to be the case. 
The shadow will be found to consist of a series of & 
light and dark stripes, as represented in FXg. 67. 
In its middle, at e, Figs. 66 and 67, there is a white Be= 
stripe; this is succeeded on each side by a dark 
one; this, again, by a bright one, and so on alternately. 

Upon the undulatory theory, all this is readily explain- 
ed. Sounds easily double round a corner, and are heard 
though an obstacle intervenes. Waves upon water _pass 
round to the back of an object on which they impinge, 
and the undulations of light in the same manner flow 
round at the back of the piece of wire, a 6, Fig. 66 ; and 
now it is plain that two series of waves which have passed 
from the sides of the obstacle to the middle of its shadow, 
that is, along the lines a e, 6 e, have gone through paths 
of equal length, and, therefore, when they encounter at 
the point e, they will not interfere, but exalt each other’s 
effect. 

But, leaving this central point, e, and passing tof, it is 
plain that the + systems of waves which have come through 
the paths a SF, &f, have come through different distances, 
for 6 fis longer than a f; and if this difference be equal 
to the length of half a wave, they will, when they encoun- 
ter at the point f, interfere and destroy each other, and a 
dark stripe results. 

Beyond this, at the point g, the waves from each side 
of the obstacles, a g, 6 g, again have come through une- 
qual paths; but, if the difference is equal to the length of 
one whole wave, they will not interfere, and a white 
stripe results. 

Reasoning in this manner, we can see that the interior 


Is the resulting shadow uniformly dark? At the central point of the 
shadow, is it dark or light?) Explain the cause of this central light space, 
and of the alternate dark and light ones on each side of it? What is the 
length of the paths of the waves which go to the illuminated spaces, and of 
those which go to the dark ones ? 


86 LENGTH OF WAVES. 


of such a shadow consists of illuminated and dark spaces 
alternately : illuminated spaces, when the light has come 
through paths that are equal, or that differ from each oth- 
er by 1, 2, 3, 4,.. &c., waves; and dark, when the dif- 
ference between them is equal to 4, 13, 23, 31,.. &c., 
waves. 

That it is the interference of the light coming from the 
opposite sides of the opaque object which is the cause of 
these phenomena, is proved by the circumstance that if 
we place an opaque screen on one side of the obstacle, so 
as to prevent the light passing, the fringes all disappear. 


LECTURE XXI. 


Wave Turory or Lienr.— Measurement of the Length of 
a Wave of Light—Length differs for different Colors. 
— Measurement of the Period of Vibrations— Nature of 
Polarized Light.— Plane, Circular, and Elliptical 
Polarized Light.—Reflection, Refraction, and Absorp- 
tion of Light. 


Tur experiment, Ig. 66, may enable us to determine 
the length of a wave of light. ‘This may be readily done 
by measuring the distances a f and b//, or from the sides 
of the obstacle to the first bright stripe from the central 
one, for at that point the difference between those two 
lines, a f and 6 f, is equal to the length of one wave. 
We might employ the second bright stripe; the differ- 
ence then would be equal to two waves. 

Farther, if, mstead of using ordinary white light, radia- 
ting from the lucid point, s, we use colored lights, such as 
red, yellow, blue, &c., in succession, we shall find that 
the wave length determined by the process just explained 
differs in each case; that it is greatest in red, and small- 
est in violet light. By exact experiments made upon 
methods more complicated than the elementary one here 
given, it has been found that the different colored rays of 
light have waves of the following length : 


How can it be proved that the waves from the opposite sides of the ob- 
stacle interfere? How, by this arrangement, might we measure the 
length of a wave of light? When different colors of light are used, are 
the waves found to be of equal length ? 


FREQUENCY OF WAVE-VIBRATION. 87 


WAVE LENGTHS OF THE DIFFERENT COLORS OF LIGHT. 
The English inch is supposed to be divided into ten 
millions of equal parts, and of those parts the wave lengths 
are : 


For red light. . . . 256 For. blae* (275 . ‘a96.2496 
“> orange. | ~ #962", 240 Mo tpeo. eas bee 
Sa rvellow? Sein >see aed *) oyaplet 3. soles. ee 2 Oe 
ae ace her ee ee 


In this manner, it is proved that the different colors of 
light arise in the ether, from its being thrown into waves 
of different lengths. 

Knowing the rate at which light is propagated in a 
second, and the wave length for a particular color, we can 
readily tell the number of vibrations executed in a second, 
for they plainly are obtained by dividing 195,000 miles, 
the rate of propagation by the wave length. From this it 
appears, that if a single second of time be divided into one 
million of equal parts, a wave of red light trembles or pul- 
sates 458 millions of times in that inconceivably short in- 
terval, and a wave of violet light 727 millions of times. 

In speaking of the constitution of matter, in Lectures I. 
and II., I had occasion to allude to the amazingly minute 
scale on which it is constructed. The remarkable facts 
we are now considering are a monument to the genius of 
Newton and his successors, for they give us a just idea of 
the scale of space and time upon which Nature carries on 
her works among the molecules of matter. 

Common light, as has been said, originates in vibratory 
motions taking place in every direction transverse to the 
ray. With polarized light it is different; to gather an 
idea of the nature of polarized light, we must refer once 
more to the cord, Fig. 62, which, as has been said, serves 
to imitate common light when its extremity is vibrated 
vertically, horizontally, and in all intermediate positions 
in rapid succession. But if we simply vibrate it up and 
down, or right and left, then it imitates polarized light; 
polarized light is, therefore, caused by vibrations trans- 
verse to the ray, but which are executed in one direction 
only. 


What is the length of a wave of red and of violet light respectively ? 
How can we ascertain the number of vibrationsin a second? On the un- 
dulatory theory, in what directions do the ethereal particles vibrate in the 
case of common light? What is the case in polarized light ? 


88 POLARIZATION OF LIGHT. i 


There is a certain gem, the tourmaline, which serves to 
exhibit the properties of polar- 
ized light. If we take a thin 
plate of this substance, c d, prop- 
erly cut and polished, and allow 
a ray of light, a b, Fig. 68, to 
fall upon it, that ray will be 
‘reely Penis! cTasespG a second plate if it be held 
symmetrically to the first, as shown ate f; but if we turn 
the second plate a quarter round, as seen at g h, then the 
light can not pass through. The rays of the meridian sun 
can not pass through a pair of: crossed tourmalines. 
Fig. 69. The cause of this is obvious: if we take 
+ @ a thin lath or strip of pasteboard, c d, 
Fig. 69, and hold it before a cage, or 
_f grate, a b, it will readily slip through 
when its plane coincides with the bars ; 
but if we turn it a quarter round, as at ¢ 
, then of course it can not pass the bars. 
Now the plate of tourmaline, Fig. 68, c d, polarizes the 
light, a 6, which falls upon it; that is, the waves that pass 
through it are vibrating all in one plane. They pass, 
therefore, readily through a second plate of the same kind, 
so long as it is held in such a way that its structure coin- 
cides with that motion, but if it be turned round so as to 
cross the waves, then they are unable to pass through it. 
There are many ways in which light can be polarized: 


o . 
by reflection, refraction, double refraction, &c. The re- 


sulting motion impressed on the ether is the same in all 
cases. 

Light modified as just described is designated plane 
polarized light; but there are other varieties of polariza- 
tion. Ifthe end of the rope, fg. 62, be moved in a cir- 
cle, circular waves will be produced, imitating circularly 
polarized light; and ifit be moved in an ellipse; elliptical 
polarized light. 

The undulstory theory of light gives a clear account ot 
the ordinary phenomena of optics. The general law 
under which light is reflected from polished surfaces is a 


Describe the optical properties of the tourmaline. Give an illustration 
of the phenomenon. What is the cause of the action of the second tour: 
maliie plate? Mention some of the methods by which light may be po- 
eed ie : iy is circularly polarized light? What is elliptically polar 

zed light 


LAWS OF REFLECTION AND REFRACTION. 89 


direct consequence of it; that lawis: thatthe | Fig. 70. 
angle, d c b, Fig. 70, made by the reflected @ b {@ 
ray, d c, with a perpendicular, ¢ 4, drawn to \ / 
the point c, at which the light impinges, is \ ; 
equal to the angle, a c b, which the incident ‘ 
ray makes with the same perpendicular, ory 
as it is briefly expressed, “ the angles of inci- 
dence and reflection are equal to each other, and on op- 
posite sides of the perpendicular.” 

By the aid of this law, we can show the action of re- 
flecting surfaces of any kind, and discover the properties 
of plane and curved mirrors, whether they be concave or 
convex, spherical, elliptical, paraboloidal, or any other 
figures. 

~From the undulatory theory, the law of the refraction 
of light also follows as a necessary consequence. It is: 
in every transparent substance, “the sines of the angles 
of incidence and refraction are to each other in a constant 
ratio ;”’ and by the aid of this law we can determine the 
action of media bounded by surfaces of any kind, plane or 
spherical, concave or convex. It explains the action of 
lenses, and the construction of refracting telescopes and 
microscopes. 

Sir Isaac Newton’s discovery, that white light arises 
from the mixture of the different colored rays in certain 
proportions, explains the cause of the colors which trans- 
parent media often exhibit; thus, if glass be stained with 
the oxide of cobalt, it allows a blue light to pass it, and 
upon such principles the art of painting on glass depends ; 
different colors being communicated by different metallic 
oxides. The cause of this effect is readily discovered ; 
for, if we make the light which enters a dark room, as in 
fig. 56, pass through such a piece of stained glass before 
it goes through the prism, and examine the resulting spec- 
trum, we find that several rays are wanting in it; that the 
glass has absorbed or detained some, and allowed others 
to traverse it. A piece of blue glass thus suffers most of 
the blue light to pass, but stops the green, the yellow, &c. 
But it is also to be observed, that the light which is trans- 
mitted by any of these colored media is not pure, it is 


What is the general law of reflection? What is the law of the refrac- 
tion of light? What is the cause of the colors of transparent media? Is 
the light transmitted through er media pure? 

2 


20 THE TITHUONIC RAYS. 


contaminated with other tints; the blue glass, for instance, 
does not stop all the rays except the blue; it allows a large 
portion of the red to pass, and hence the light it transmits 
is more or less compound. 


LECTURE XXII. 


Tue Tirnonic Rays.—Peculiarities of the Tithonic Rays. 
—Thew Physical Independence of Heat and Light— 
Analogies with Light.—Found in Moonlight, Lamp- 
light, §c—Preliminary Absorption and definite Action. 
—In producing a Chemical Effect, the Ray changes.— 
Daguerreotype—Application to taking Portraits.—Na- 
ture of the Daguerreotype.— Other Photogenic Processes. 


Ir has been already observed, that when a solar spec- 
trum falls upon paper covered over with chloride of sil- 
ver, the chloride turns black in the more refrangible re- 
gions, and from this and similar experiments we have been 
led to the knowledge that there exists in the sunbeam a 
principle which can bring about chemical changes. 

This fact has been received from the beginning of the 
present century; but, of late, much attention has been 
given to these rays, and from a consideration of the phe- 
nomena they exhibit, I have endeavored to prove that they 
constitute a fourth imponderable principle of the same 
rank as heat, light, and electricity; and, for the purpose 
of giving precision to this view, have proposed that they 
should be called Tithonic rays, from the circumstance 
that they are always associated with light; drawing the 
allusion from the classical fable of Tithonus and Aurora. 

This name is, however, to be regarded as a provisional 
one. Every thing seems to indicate that sooner or later 
all these principles will be reduced to one of a more gen- 
eral nature, or that they are all modifications of move- 
ments taking place in the ether. 

The evidence of the physical independence of the Ti- 
thonic rays is very much of the same character as the evi- 
dence of the difference between heat and light. These 


What reason have we to suppose that there exists another principle 
besides heat and light in the solar rays? Why is the name Tithonic rays 
suggested for this principle ? 


PROPERTIES OF THE TITHONIC RAYS. 91 


rays are invisible to the eye, and therefore are not light; 
they do not affect a thermometer, and therefore are not 
heat. Media which are transparent to heat are not trans- 
parent to them, and media through which light readily 
passes are perfectly opaque to them. 

The Tithonic rays are emitted, and undergo reflection, 
refraction, and polarization, precisely in the manner of 
‘light and heat. Unlike the latter principle, they exhibit 
no phenomenon of conduction; the effect which they pro- 
duce does not pass from particle to particle, but is limited 
to that on which the light has impinged ; nor is it, as yet, 
distinctly established that they exhibit any phenomenon 
analogous to secondary radiation. An object upon which 
rays of heat fall, as it becomes warm, radiates back again, 
but a substance on which Tithonic rays are impinging 
does not radiate in like manner. 

In the sunbeams Tithonic rays exist abundantly; I have 
also found them in the moonlight, in sufficient quantity to 
give copies of that satellite on sensitive surfaces. In 
lamplight and other artificial light, they also occur to a 
much greater extent than is commonly supposed. They 
do not effect a thermometer, because, except under pe- 
culiar circumstances, they can not produce expansion ; 
their office appears to be to arrange and group the mole- 
cules of bodies, and to bring about the substitution of one 
element for another. 

When the Tithonic rays fall upon a sensitive medium 
for a brief space of time, no change takes place in it; 
during this time the rays are actively absorbed, but as 
‘soon as that preliminary absorption is over they act in a 
manner which is perfectly definite: if, for instance, it be 
a decomposition they are bringing about, the amount of 
decomposing effect will be precisely proportional to the 
quantity of rays absorbed. 

When a beam from any shining source causes a de- 
composing effect, it is uniformly observed that it is itself 
disturbed; the medium which is changing impresses a 
change on the ray. Thus, a mixture of chlorine and hy- 


t 
Are these rays visible? Do they affect a thermometer? Can they be 
conducted like heat? Do they exhibit secondary radiation? Are they 
found in the moonbeams and artificial lights? Do they affect the ther- 
mometer? The mode of action of these rays on bodies is divided into two 
oree® what arethey? Does the ray itself change in bringing about these 
chans=9 ” 


92 THE DAGUERREOTYPE. 


drogen unites under the influence of a ray, but that por- 
tion of the ray which passes through the mixture has lost 
the quality of ever bringing about a like change again; 
the mixture is tithonized and the light detithonized. 

When a beam from any shining source falls on a 
changeable medium, a portion of it is absorbed for the 
purpose of effecting the change, and the residue is either 
reflected or transmitted, and is perfectly inert as respects 
the medium itself. 

No chemical effect can, therefore, be produced by such 
rays except they be absorbed. It is for this reason that 
water is never decomposed by the sunshine, nor oxygen 
and hydrogen made to unite; for these substances are all 
transparent, and allow the rays to pass without any ab- 
sorption, and absorption is absolutely necessary before 
chemical action can ensue. 

But with chlorine the case is very different. This sub- 
stance exerts a powerful absorbent action on light; the 
effect takes place on the more refrangible rays; when 
mixed with hydrogen and set in the light, it unites with a 
violent explosion. 

The process of the Daguerreotype depends on the action 
of the Tithonic rays. It is conducted as follows: A piece 
of silver plate is brought to a high polish by rubbing it 
with powders, such as ‘l'ripoli and rotten-stone, every care 
being taken that the surface shall be absolutely pure and 
clean, a condition obtained in various ways by different 
artists, as by the aid of alcohol, dilute nitric acid, &c. 
This plate is next exposed in a box to the vapor which 
rises from iodine at common temperatures, until it has ac- 
quired a golden yellow tarnish; it is next exposed, in the 
camera obscura, to the images of the objects it is designed 
to copy, for a suitable space of time. On being removed 
from the instrument, nothing is visible upon it; but on ex- 
posing it to the fumes of mercury, the images slowly evolve 
themselves. 

To prevent any farther change, the tarnished aspect of 
the plate is removed by washing the plate in a solution of 
hyposulphite of soda, and finishing the washing with wa- 
ter; it can then be kept for any length of time. 


Does the ray undergo absorption? Why can not water be decomposed 
in the sunshine? Why do chlorine and hydrogen explode? Describe 
the process of the Daguerreotype. Are the images visible at first? By 
what means are they brought out? How is the picture preserved from 
farther change ? 


PHOTOGENIC PORTRAITS. 93 


Several important improvements on the original process 
have been made: Ist, by exposing the plate, after it has 
been iodized, to the vapor of bromine, or chloride of iodine, 
which gives it a wonderful sensibility ; 2d, by gilding the 
plate, after the other operations are complete, by the aid 
of a mixture of hyposulphite of soda and chloride of gold ; 
this acts like a varnish, fastening the picture and giving 
it a more agreeable yellow tone. 

The art of taking portraits from the life, which has now 
become a branch of industry, was invented by me soon 
after the Daguerreotype was known in America; at that 
time, this, which is by far the most valuable application 
of the chemical agencies of light, was looked upon in Eu- 
rope as entirely beyond the powers of this process; but 
subsequently great improvements in it have been made. 
My memoir descriptive of the art may be seen in the Lon- 
don and Edinburgh Philosophical Magazine (September, 
1840), and the facts are also specified in the Edinburgh 
Review (January, 1843), in which the discovery is attrib- 
uted to its proper source, the author of this book. 

When a beam falls upon the surface of a: Daguerreotype 
plate, it communicates to the iodide of silver a tendency 
to decomposition, but iodine is never set free because of 
the metallic silver behind. On exposing a surface dis- 
turbed in this manner to the vapors of mercury, entire 
decomposition of the iodide ensues, its silver unites with 
the mercury, forming a white amalgam, and the iodine 
corrodes the metallic silver behind. The utmost care 
must be taken in all Daguerreotype processes to have no 
vapors of iodine, or bromine, or chlorine about the camera 
or other apparatus; they possess the quality of effacing 
the effects of light, and the most common source of failure 
among Daguerreotype artists is due to neglecting this 
precaution. 

There are some important difficulties to which the Da- 
guerreotype is liable. For taking landscapes it is not 
available. Green and red colors impress no change upon 
it. The order of colors and light and shadow is not, there- 
fore, strictly observed. 


Mention some of the later improvements of the process? In this pro- 
cess is iodine set free from the plate? With what does the iodine unite 
under the influence of the mercurial vapor? Why is not the Daguerreo- 
type applicable to landscapes ? 


94 IDEAL COLORATION. 


There are many other photogenic processes now known: 
several have been invented by Mr. Talbot; among them 
may be mentioned the calotype. Sir J. Herschel, also, 
has discovered very beautiful ones, and these possess the 
great advantage over Daguerre’s that they yield pictures 
upon paper. In minuteness of effect they can not, howev- 


er, be compared to the Daguerreotype. 


LECTURE XXIII. 


Tuerory oF Iprau Coitorarion.—Imaginary Coloration. 
— Variation in the Colors of radiant Heat as the Temper- 
ature changes.—Ideal Coloration of natural Objects.— 
Eixed Lines in the Spectrum.—Phosphorogenic Rays.— 
Relations of the radiant Principles to the Vegetable 
World.—Spectral Impressions. 


In explaining the discoveries made by M. Melloni in 
relation to radiant heat (Lecture XV.), we had occasion 
to observe the difference between the action of glass and 
rock salt in their quality of transparency, and it was stated 
that the phenomenon is due to differences in the nature 
of the heat analogous to the different colors of light. As 
these modifications are found also in the Tithonic rays, and 
as neither these nor the rays of heat are visible to the eye, 


I have suggested the use of the term ideal or imaginary 


coloration, as expressing the facts we have now under 
consideration. 
By the theory of ideal coloration we mean, that as 


.there are modifications of light constituting the seven 


primitive colors, red, orange, yellow, green, blue, indigo, 
and violet, so, too, chore are similar modifications of the 
other invisible principles of the spectrum, differing from 
each other by the length of the waves which constitute 
them; and also, that as natural bodies exhibit to our 
eyes a variety of colors, so, in the same manner, they are 
colored as respects these invisible principles, Hit the col- 
oration under these circumstances is different from these 
colorations for light. 


—_— 


What is meant by ideal coloration? Do natural bodies possess colora 
tion for the other principles of the sunbeam as well as light? Is their ool- 
or the same in these cases? 


IMAGINARY COLORS OF BODIES. 95 


To make this plain, let us take an illustration: glass 
is colorless and transparent to light, and allows any kind 
of light-ray to traverse it with facility; but to heat, com- 
ing from sources of a low temperature, it is wholly opaque. 
And this arises from the circumstance that the rays of heat 
which come from such a source are constituted of short 
waves, and therefore bear an analogy to violet light, 
while glass acts toward the heat as a ruddy or orange-col- 
ored medium. The reason, therefore, that this heat of 
low temperature can not go through glass is because it is 
of a violet color, while the glass is red. But as the tem- 
perature rises, calorific rays of other tints begin to be 
emitted, yellow and red successively, and these easily find. 
passage through the medium. 

To the rays of heat, rock salt is a white body, glass 
orange, and alum deep red. The color of these bodies 
for heat is not the same as their color for light; and as 
the eye can not detect the phenomenon directly, we speak 
of it as imaginary or ideal coloration. 

Radiant heat undergoes polarization after the manner 
of light; the wave mechanism is the same in both cases. 

The Tithonic rays, also, exhibit all the phenomena due 
to imaginary coloration, and they may therefore be spoken 
of as violet, yellow, green, and Tithonic rays. To them 
the various objects of nature have a peculiar coloration. 
The bromide of silver is yellowish-white as respects light, 
but black to these rays. 


As respects the fixed lines discovered in the luminous. . 


spectrum, as represented in fg. 59, they also occur in 
the impressions left upon sensitive surfaces on which the 
spectrum is received, as was discovered by M. Bequerel 
and myself about the same time (1842). In this instance, 
however, they are far more numerous, and occur in groups 
of many hundreds beyond the visible limits of the violet 
ray. 

It has already been mentioned that there is associated 
with the light derived from shining sources an invisible 
principle, which causes the phosphorescence of many 
bodies. Thus, if oyster-shells be calcined with sulphur 


Why does glass change its transparency for radiant heat? What is 


the color of rock salt, alum, and glass for heat? Can radiant heat be po- 
larized? What is the color of bromide of silver for light rays and 'Ti- 
thonic rays respectively? Can the fixed lines be obtained on sensitive 
surfaces? Give some instances of phosphorescent bodies. 


4 


96 PHOSPHORESCENCE. 


and exposed to the sun, they shine for a considerable time 
after in the dark. Nor does it require that the time of 
exposure should be protracted ; the flash of an electric 
spark is sufficient. But, what is very remarkable in this 
case, the rays which excite the phosphorescence can not 
pass through a piece of colorless glass; to them it is quite 
opaque. ‘The experiments of Mr. Wilson show that a 
great number of bodies not commonly supposed to be 
phosphorescent are so in reality ; that for a few moments 
after they have been exposed to the sun, they emit a phos- 
phorescent light. Thus, a sheet of writing paper, on which 
a key had been laid, having been exposed for a few mo- 
ments to the sun, on being suddenly removed to a dark 
room emitted a pale light, the shadow of the key being 
perfectly visible. Even the hand, after being dipped in 
the sunshine, emitted subsequently light enough to be 
visible in a dark place. 

The various principles of which we have been speak- 
ing exert no ordinary control over the phenomena of the 
natural world. Thus it is to the influence of light that 
the vegetable world owes its existence; for plants can 
only obtain carbon from the air while the sun is shining 
on them, and it is of that carbon that their solid structures 
are chiefly formed. It has been a question to which prin- 
ciple this effect is due; but, in 1843, I proved that it is 
the yellow light which is involyed. Dr. Priestley discov- 
ered that the leaves of plants will effect the, decomposi- 
tion of carbonic acid gas under water; and on immersing 
tubes filled with water holding this gas in solution, and 
containing a few green leaves, I found that at the blue 
extremity of the spectrum no effect whatever took place, 
while decomposition went on rapidly in the yellow ray. 
It is light, in contradistinction to other principles, which is 
the agent producing this result, and of its colored modifi- 
cations the yellow ray is the most active. 

As connected with the minute changes of surface which 
are effected when the different radiant principles fall upon 
bodies, as in the instance of the Daguerreotype, we may 
here allude to the formation of spectral ampressions, which, 
though invisible, may be brought out by proper processes. 


What is the relation of light to the vegetable world? What color forms 
the active ray? What was Dr. Priestley’s discovery? What is meant 
by spectral impressions ? 


ELECTRICITY. 97 


One of these I described several years ago. Take a piece 
of polished metal, glass, or japanned tin, the temperature 
of which is low, and having laid upon it a wafer, coin, or 
any other such object, breathe upon the surface; allow 
the breath entirely to disappear ; then toss the object off 
the surface and examine it minutely; no trace of any 
thing is visible, yet a spectral impression exists on that 
surface, which may be evoked by breathing upon it. A 
form resembling the object at once peat and, what is 
very remarkable, it may be called forth many times in 
succession, and even at the end of many months. Other 
instances ofthe kind have subsequently been described 
by M. Moser. 


~ 


LECTURE XXIV. 


Evecrricity.— First Observations in Electricity.—De- 
scription of Electrical Machines — The Spark a Test of 
Electrical Excitement.—Repulsion of Electrified Bodies. 
—Simple Means of Excitement— Conductors and Non- 
conductors. — Insulation.— Electric Effects take place 
through Glass — Medicated Tubes. 


“ 


Ir was observed, six hundred years before Christ, that 
a piece of amber, when rubbed, acquired the quality of 
attracting light bodies. This fact remained without value 
for more than two thousand years, a striking memorial of 
the barren nature of the philosophy of-those times. With- 
in the last two hundred years it has given birth to an en- 
tire group of sciences, and established the existence of a 
great imponderable principle, which, from the Greek 
word 7Aextpov, signifying amber, has taken the name 
ELecrricirty. 

The catalogue of substances in which electric develop- 
ment can be produced was greatly increased by Gilbert, 
who showed that glass, resin, wax, and many other bodies, * 
are equally effective as amber. To his successors we owe 
the electrical machine, an instrument which enables us 
readily to demonstrate the properties of electricity. 


Give an example. What was the first observation made in electricity ? 
From what does the agent derive its name? an 


98 ELECTRICAL MACHINES. 


Electrical machines are of dif- 
ferent kinds. They may, how- 
ever, be divided into plate and 
cylinder machines. These instru- 
ments are respectively represent- 
ed in Fig. 71 and Fig. 72. In 
each of them there are three dis- 
tinct portions. First, a piece of 
glass, the shape of which differs 
in different cases; in Fig. 71 it 
is a circular plate, in Pig. 72 a 
cylinder; and from these the in- 
struments take their name. Sec- 
ond, the rubbers, made of silk or leather, stuffed with 
hair: the office of these is 
to press lightly on the glass 
_ 28-it turns round, and pro- 
duce friction. Third, a 
brass body, of a cylindri- 
cal or rounded shape, but 
with points on that portion 
of it which looks toward 
the glass. It is support- 
ed on glass props, and is 

e termed the prime conduct- 
or. saint mechanism, such as a winch, is required to 
turn the glass on its axis; and when it is detvod to bring 
the machine into activity, all the parts of it having been 
made thoroughly clean and dry by rubbing with a piece 
of warm silk or flannel, a little Mosaic gold or amalgam 
of zinc being spread on the rubber, as soon as the winch 
is turned the instrument becomes excited. 

One of the most striking manifestations of electrical 
development is the spark; this, which must have been 
often seen when the back of the domestic cat is rubbed on 
a frosty night, was first discovered in the case of glass or 
sulphur, by Otto Guericke, and by him referred to its 
proper source, electric excitement. On presenting a brass 
ball or the finger to the prime conductor of the machine, 
the spark passes, attended with aslight report. It may be 


Fig. 72. 


What varieties of electrical machines have we? What are the three 
essential parts of these machines? What is the rabber? What is the 
prime conductor? How is the machine excited? 


ELECTRICAL LIGHT AND REPULSION. 99 


very beautifully shown by pasting Fig. 73. 
small pieces of tin foil round a glass OS 
tube in a spiral form, as shown i in a 
Fig. 73, abe, distalices of the twentieth of am inch 1 ate 
vening between each piece, and the ends of the tube ter- 
minated by balls. On presenting one of these balls to the 
prime conductor, and holding the other in the hand, as 
the spark passes, it has to leap over each interstice be- 
tween the spangles of tin foil, and exhibits a beautiful 
spiral line of light. 

By pasting the tin foil on a pane of glass in such a 
way as to direct the spark Fig. 74. 
properly, words may be written 
in electric light, as shown in @| 
Fig. 74, 

As the electric spark can 
scarcely be confounded with any other Pig ei 
enon whatever, its presence is always indubitable evi- 
dence of electric excitement. ‘Thus, we can prove that 
electricity may be transferred to the human body from 
the machine, by placing a man on a 
stool supported by glass pillars, Fg. 
75. Ifhe touches the prime conductor 
with one hand, sparks may be drawn 
from any part of his clothing or body. \f_ 

To Otto Guericke, who was alsothe ~ = , 
inventor of the air pump, we owe another of the most im- 
portant discoveries in electricity: that bodies 5, 76, 
which have touched an excited substance are 
subsequently repelled by it; thus, if we rub 
a glass tube, Fig. 76, a, until it becomes elec- 
trified, and then present it to a feather, 3, 

Fig.77. | Suspended by a silk thread to a 

stand, c, the feather is at first at- 

. tracted, and then immediately re- 
\ ‘pelled. Nal 
On this principle, that under certain circum- 
stances repulsion takes place, are founded dif- 
ferent methods for ascertaining the existence 


-. Fig. 75. 


——— 
SST 


= 
we] 
) 


aéb 


How may the electric spark be exhibited? Why may it be used as a 
test for electric excitement? Can electricity be transferred from the 
machine to the body? What discovery did Otto Guericke make in elec- 
tricity? How may this property of repulsion be illustrated ? 


100 CONDUCTORS AND NON-CONDUCTORS. 


of electric excitement, when too feeble to cause a spark. 
Thus, two light balls of cork, Fig. 77 (p. 99), a 6, sus- 
pended by linen threads so as to hang side by side, as 
soon as they are electrified repel each other. 

It does not, however, require an electrical machine to 
demonstrate the principles of this agent. A piece of stout 
brown paper three inches wide, and a foot long, if held 
before the fire until it is quite dry and smokes, and then 
drawn between the knee and the sleeve, becomes highly 
excited, especially if the person wears woollen clothing. 
It will yield sparks more than an inch long. 

Let a, Fig. 78, be the termination of the prime conduct- 


Fig. 78. or, and in a hole in it place the long 
bs b ¢ brass rod 6, terminated by the brass 
aw) ? ballc. If the finger is approached to 


the ball, sparks freely pass, showing that along brass elec- 
tricity is conducted ; but if a glass rod of the same diam- 
eter and length, and terminated by a brass ball, be em- 
ployed, not a solitary spark can be obtained, proving that 
glass is a non-conductor of electricity. 

The important fact that substances may be divided into 
two classes, conductors and non-conductors, was first ac- 
cidentally discovered by Dr. Grey, who found that all 
metals and moist bodies are conductors, and that glass, 
resins, wax, sulphur, atmospheric air, are non-conductors. 
In the treatises on chemistry, tables may be found exhibit- 
ing the relations of bodies in this respect. ‘The conduct- 
ing power of the same substance differs with circumstan- 
ces; thus, ice and glass are non-conductors, but water and 
melted glass are conductors. 

We see, from these facts, the explanation of the struc- 
ture of the prime conductor; the electricity derived from 
the glass by friction passes easily along the brass portion, 
but can not escape into the earth, owing to the glass sup- 
ports, which refuse it a passage. When a body is thus 
placed upon glass, it is said to be electrically insulated, 
and the process is called insulation. 

Although electricity can not pass through glass, Sir 
Isaac Newton found that this substance is no impediment 


By what simple means may electrical experiments be made? How 
may it be proved that brass is.a conductor and glass a non-conductor ? 
Mention some of the leading substances belonging to each of these classes. 
Explain the structure of the prime conductor. Can electric influences 
pass through glass ? / 


TWO SPECIES OF ELECTRICITY. 101 


to the exertion of its influences. Thus, ceo 
; 3 g. 79. 

in rg. 79, if @ be the brass ball of the a 
prime conductor, any light objects, such ee 
as bits of paper or fragments of cork, 
placed on a metal stand, 4, beneath will 
be attracted ; and though a pane of 
glass, c, be placed between a and 4, still 
the same phenomenon takes place. 

Soon after electricity became a subject of popular at- 
tention, it was currently believed, that if medicines of va- 
rious kinds were sealed up in glass tubes, and the tubes 
electrically excited, their peculiar virtues would be exhal- 
ed in such a manner as to impress the operator with their 
specific purgative, emetic, or other powers. Like many 
of the popular delusions of our times, this imposture was 
supported by the most cogent evidence, and maladies cur- 
ed publicly all over Europe. Like them, these ‘* medica- 
ted tubes” have served to prove the worthlessness of hu- 
man testimony when derived from the prejudiced and 
ignorant. 


LECTURE XXV. 


TuHeory or Exvrcrrican Inpuction.—Two Species of 
Electricity — Their Names.— General Law of Attraction 
and Repulsion— Theory of Induction —Permanent Ex- 
citement by Induction.— Takes place through Glass— 
Illustrative Experiments. 


A very celebrated French electrician, Dufay, having 
caused a light, downy feather to be repelled by an excit- 
ed glass tube, intended to amuse himself by chasing it 
round the room with a piece of excited sealing-wax. To 
his surprise, instead of being repelled, the feather was at 
once attracted. On examining the cause of this more mi- 
nutely, he arrived at the conclusion that there are two 
species of electricity, the one originating when glass is 
excited, and the other from resin or wax. To these he 
gave the names of vitreous and resinous electricity, thus 


What was formerly meant by medicated tubes? How was it first dis- 
covered that there are two species of electricity? What names have 
been given to these electricities ? a 

12 


102 ELECTRICAL INDUCTION. 


pointing out their origin; they are also called, for reasons 
which will be given hereafter, positive and negative elec- 
tricities. 

He found that these different electricities possess the 
same general physical qualities; they are self-repulsive, 
but the one is attractive of the other. ‘This is readily 
proved by hanging a feather by a linen thread to the prime 
conductor of the machine, and, when it is excited, bringing 
near to it an excited glass tube. The feather is already 
vitreously electrified, and the tube, being in the same con- 
dition, at once repels it; but a stick of excited sealing- 
wax being resinously electrified, that is to say, in the 
opposite condition to the feather, at once attracts it. 
Two cork balls, as in Fug. 77, suspended by conducting 
threads, always repel one another when both are excited 
either vitreously or resinously ; but if one be vitreous and 
the other resinous, they attract. 

These various results may all be grouped under the 
following general law, which includes the explanation of a 
great many electrical phenomena. Bodies electrified dis- 
similarly attract, and bodies electrified similarly repel; or, 
more briefly, like electricities repel, and unlike ones attract. 

There are many ways in which electrical excitement 
can be developed: in the common machine it is by fric- 
tion ; in the tourmaline, a crystallized gem, by heat; and in 
other cases by chemical action and by conduction. Elec- 
trical disturbance also very often arises from induction. 

By the term electrical induction we mean that a body 
which is already excited tends to disturb the condition of 
others in its neighborhood, inducing in them an electric 
condition. 

Thus, let a, Fig. 80, bé the terminal ball of the prime 

Fig. 80. conductor, and a few inches 
off let there be placed a sec- 
ondary conductor, &c, of brass 
supported on a glass stand, and 
at each extremity, 6 and c, of 
the conductor, let there be ar- 
ranged a pair of cork balls 


What are their physical qualities? How may this self-repulsion and 
mutual attraction be proved? What is the general law of electric attrac- 
tions and repulsions ? In what ways may electric excitements be devel-- 
oped? What is the meaning of electric induction? Give an illustration. 


ELECTRICAL INDUCTION. 103 


suspended by linen threads, as shown in the figure. As 
‘soon as the ball, a, is electrified by turning the machine, 
and without any spark passing from it to the secondary 
conductor, the balls will begin to diverge, showing that 
the condition of that conductor is disturbed by the neigh- 
borhood of the excited ball, a. 

It will farther be found, on presenting an excited piece 
of sealing wax to the pairs of cork balls, that one set is 
attracted, and the other repelled. They are, therefore, in 
opposite electrical states. The disturbing ball is vitre- 
ously electrified, and that end of the secondary conductor 
nearest it is resinous, the farther end being vitreous. If 
the disturbing ball, a, be now removed, the electric dis- 
turbance ceases, and the corks no longer diverge. 

These phenomena of electric induction are not depend- 
ent on the shape of bodies. Let there be Fig. 81. 
two flat circular plates, a 6, Fig. 81, sup- 55 
ported on glass stands, and set a few inches 
apart, looking face to face. Let one of them, 
a, be electrified positively by contact with 
the prime conductor, as indicated by the 
sign +; it immediately induces a change 
in the opposite plate, the nearest face of 
which becomes negative —, and the more distant, positive. 
It is evident that this disturbance is a consequence of the 
law, that “like electricities repel, and unlike ones attract.” 
In the plate 4, both species of electricity exist, and a be- 
ing made positive, even though at a distance, exerts its 
attractive and repulsive agencies on the electric fluid of 
b, the negative electricity of which it attracts, and draws 
near to it; the positive it repels. and drives to the farthest 
side ; so that the disturbed condition of the body 6 is a 
result of the fact, that @ being electrified positively, will 
repel positive electricity and attract negative. 

Now let the plate 6 be touched by the finger, or a 

“tehannel of communication opened with the earth; the 
positive electricity of a still exerting its repulsive agency 
on that of 4, will drive it into the ground, and 4 will now 
become negative all over. - 

Let 4 be once more insulated, by breaking its commu- 


In a secondary conductor disturbed by an electrified body, what are the 
conditions of its ends? What is the cause of this disturbance? How 
may we by induction permanently electrify a body? 


104 MISCELLANEOUS EXPERIMENTS. 


nication with the ground, and let a be removed; it will 
now be found that 4 is permanently electrified, and.in the 
opposite condition to a. 

By manipulating in this manner, we can, therefore, ef- 

Fig. 82. fect a permanent disturbance in the Gendition 
of an insulated body, by bringing an excited one 
in its neighborhood. 

In these changes, the intervention of a piece 
of glass makes no difference. Let a circular 
plate of glass, a, Fug. 82, be set so as to inter 
vene between the metallic plates, a and 4, and 
still all the phenomena occur as before. Elec- 
tric induction, therefore, can take place through glass. 

Fig. 83. On the principles of induction, and of electric 
attraction and repulsion, many very interesting 
experiments may be explained. The following 
may serve as examples: ‘T’o the ball of the prime 
conductor, fg. 83, let there be suspended a cir- 
cular plate of “brass, a, six inches in diameter, 
horizontally, and beneath it another plate, 4, 
supported on a conducting foot, parallel and ata 
distance of three or four inches. On the lower 
plate, 6, place slips of paper or of other light 
substance, cut into the figure of men or animals. On set- 
ting the machine in motion, so as to electrify the upper 
plate, the objects move up and down with a dancing mo- 
tion; and the cause is obvious: the plate a being posi- 
tive, repels by induction the positive electricity of the 
figures through the conducting stand into the earth, and 
thus, they being rendered negative, are attracted by the 
upper plate ; on touching it, they become electrified posi- 
tively like it, and then are repelled, and fall down to dis- 
charge their electricity into the ground, 
-and this motion is continually repeated. 
Upon a horizontal brass bar, a 6, Fig. 
’ 84, three bells are suspended, the outer 
ones at a and 3} by chains, the middle 
f one at c bya silk thread. Between the 
n= bells, the metallic cl d . 
wees, Dells, the appers, d e, are sus 

~ pended by silk, and from the center bell 


Can electrical induction take place through glass? Describe the ex- 
Ae of the dancing figures, and explain ‘the principles involved in it. 
escribe the experiment of the bells, and the cause of their ringing. 


MISCELLANEOUS EXPERIMENTS. 105 


the chain f extends to the table. On hanging the ar- 
rangement by the hook at § to the prime conductor, the 
bells ring ; the clappers moving from the outer to the cen- 
tral bell and back, alternately striking them. 

On a pivot, a, Fig. 85, suspend a bell jar having four 
pieces of tin foil pasted on its 
sides, 6 c d; connect the jar, by 
means of the insulated wire y, with 
the prime conductor, so that the 
pieces of tin foil may receive 
sparks. On the opposite side ar- 
range a conductor, x, in connection 
with the ground by a chain. On {§ 
putting the machine into activity, 
the jar will commence rotating on its pivot. 

Take a cake of sealing wax or gum lac, eight or ten 
inches in diameter, and receive on its surface a fow sparks 
from the prime conductor by bringing it near the ball. 
Then blow upon its surface from a small pair of bellows, 
a mixture of flowers of sulphur and red-lead, which have 
been intimately ground together in a mortar. This mix- 
ture is of an orange color, but the moment it impinges on 
the cake it is, as it were, decomposed; the yellow sulphur 
settling on one portion, and the red-led on another, giv- 
ing rise to very curious and fantastical figures. 


LECTURE XXVI. 


Laws oF THE DISTRIBUTION oF ELECTRICITY, AND THE 
GENERAL THEor1ES.— Distribution of Electricity —On 
a Sphere.—Ellipsoid.—Action of Points —Franklin’s 
Discovery of the Identity of Electricity and Lightning. 
— The Leyden Jar.— The discharging Rod.— The Elec- 
tric Battery. 


WueEn electricity is communicated to a conducting body, 
it does not distribute itself uniformly through the whole 
mass, but exclusively upon the surface; thus, if to the 


Explain the arrangement and cause of movement of the rotatory jar. 
How may powder of sulphur and red-lead mixed together be separated ? 
Does electricity distribute itself on the surface or in the interior of bodies ? 


106 DISTRIBUTION OF ELECTRICITY. 


spherical ball a, Fig. 86, supported 
on an insulating foot, 4, there be 
, adjusted two hemispherical caps, 
cc, also on insulating handles, it 
may be proved that any electricity 
communicated to a distributes itself 
entirely on its surface; for if we 
place upon a the caps cc, and then remove them, it will be 
found that every trace of electricity has disappeared from 
a, and has accumulated on the caps, which, while they 
were upon the ball, formed its superficies. 
Fig. 81. Again, if we take a large brass ball, a, Fig. 87, 
supported on an insulating stand, and having on 
. its upper portion an aperture, 4, through which 
D we may have access to its interior, it will be found, 
#“ on examination, that the most delicate electrom- 
eters can discover no electricity within the ball, 
the whole of it being on the external superficies. 
In the case of a spherical body, not only is the 
distribution entirely superficial, but it is also uni- 
form; each portion of the sphere is electrified alike. But 
where, instead of a spherical, we have an ellipsoidal body, 
it is different; thus, if we examine the condition of such 
Fig. 88. a conductor, gure 88, the quantity 
of electricity in its middle portion, 
as at a, will be the smallest,” and 
it increases as we advance toward 
the ends, 6 and c; and in different 
ellipsoids, as the length becomes 
greater, so the amount of electricity 
found on the extremities is greater, 
When, therefore, a conductor of an 
oblong spheroidal shape is used, the intensity of the elec- 
tricity at the extremities of the two axes, ad and bc, Fig. 
88, is exactly in the proportion of the length of those axes 
themselves ; and should the disproportion in length and 
breadth of the conducting body be very great, as in the 
case of a long wire or other pointed body, a very great 
concentration will take place upon the points. On this 


How may its superficial distribution be proved? In the interior of an 
electrified hollow ball, does any electricity exist? On a spherical body, 
is the distribution uniform? How is it on an ellipsoid? When the dis- 
proportion of the axes of the ellipsoid is great, what is the distribution ? 


IDENTITY OF LIGHTNING AND ELECTRICITY. 107 


principle we explain the effect of pointed bodies on con- 
ductors: if the prime conductor of the machine have a 
needle or pin fixed upon it, the electricity escapes away 
into the air, visibly in a dark room; and in the same way, 
if pointed bodies surround the electrical machine, it can 
not be highly excited, as they rapidly take the charge from 
its conductor. 

At a very early period electricians had observed the 
close similarity between the phenomena of the electric 
spark and those of lightning, but in the year 1752 Dr. 
Franklin proved that they were identical. He was waiting 
for the erection of the spire of a church in Philadelphia, on 
the extremity of which he intended to raise a pointed metal 
rod, with a view of withdrawing the electricity from the 
clouds, when the accidental sight of a boy’s kite suggested 
to him that ready means of obtaining access to the more 
elevated regions of the air. Accordingly, having stretched 
a silk handkerchief over a light wooden cross, and ar- 
ranged it as a kite, he attached to it a hempen string ter- 
minating in a silk cord, and, taking advantage of a thunder 
storm, raised it in the air; for a time no result was ob- 
tained, but the string becoming wet by the rain, and there- 
by rendered a better conductor, he perceived the filaments 
which hung upon it repelling one another, and on present- 
ing his knuckle to a key which had been tied to the end 
of the hempen string, received an electric spark. The 
identity of lightning and electricity was proved. 

Franklin soon made a useful application of his discov- 
ery; he proposed to protect buildings from the effects of 
lightning by furnishing them with a metallic rod, pointed 
at its upper extremity and projecting some feet above the 
highest part of the building, and continuously extending 
downward until it was deeply buried in the ground. This 
contrivance, the lightning rod, is now, as is well known, 
extensively applied. 

There are two theories respecting the nature of elec- 
tricity: 1st, Franklin’s theory, which assumes that there 
is but one fluid; 2d, the theory of two fluids, called also 
Dufay’s theory. 


How may we explain the effect of pointed bodies? Under what cir- 
cumstances was the discovery of the identity of lightning and electricity 
made? ‘What is the lightning rod? What theories of electricity have 
been introduced ? 


a 
108 THEORIES OF ELECTRICITY. 


Franklin’s theory is, that there exists throughout all. 
space a subtle and exceedingly elastic fluid, called the 
electric fluid, the peculiarity of which is, that, it is repuls- 
ive of its own particles, but attractive of the particles of 
other matter; that there is a specific quantity of this 
fluid which bodies are disposed to assume when in a nat- 
ural condition or state of equilibrium; and that, if we com- 
municate to them more than their natural quantity, they 
become positively electrified; or, if we take from a portion 
of that which is natural to them, they become negatively 
electrified. 

Dufay’s theory is, that there exists throughout all space 
a universal medium, called the electric fluid, of which 
the immediate properties are unknown, but which is com- 
posed of two species or varieties of electricity, the vitreous 
and resinous, called also the positive and negative ; that, 
as respects itself, each of these electricities is repulsive, 
but attractive of the other kind; and that, when they co- 
exist In equal quantities in a body, it is in a neutral state 
or condition of equihbrium, but if the positive or negative 
electricities are in excess, it is accordingly positively or 
negatively electrified. _ 

In some respects the theory of two electricities has ad- 
vantages over that of one; by it several phenomena can be 
explained which are difficult of explanation by the other. 
Among such may be mentioned the repulsion of negatively 
electrified bodies, and the distribution of negative elec- 
tricity on the surface of conductors, which is the same as 
that of positive. 

On the principles of either of these theories we can 
see how it is that we can never produce one kind of elec- 
tricity without the other simultaneously appearing. In 
the common electrical machine, if the revolving glass is 
positively electrified, the rubbers which produce the fric- 
tion are negative; in the tourmaline, if one end of the 
crystal, when warmed, becomes positive, the other end is 
negative. The two varieties must be always co-ordinately 
generated. 

In 1745 the Leyden jar was discovered. This consists 
of a glass jar, Fig. 89, coated on its inside with a piece 


What is Franklin’s theory? What is the theory of Dufay? In what 
points does the latter appear to be more correct than the former? Why 
are both electricities always produced together? 


. 


THE LEYDEN JAR. 109 


of tin foil within an inch or two of its upper Fig. 89. 
edge, and also on its outside to the same point; 
through the cork which closes the mouth of 
the jar, a brass rod, terminated by a ball, 
passes; the rod reaches down to the inside 
coating and touches it. On holding this in- 
strument by the exterior coating, and pre- 


senting its ball to the prime conductor, a tor- 
rent of sparks passes into the jar; and when § 
it is fully charged, if, still retaining one hand “~~ 
in contact with the outside, we touch the ball, a bright 
spark passes, with a loud snapping noise, and the operator 
receives through his arms and breast what is called the 
electric shock, 

If we take the discharging rod, Fg. 90, consisting iz. 99, 
of two brass arms, a a, terminated by balls working g ¢ 
on a joint, 6, and supported by an insulating handle, 
c, by bringing one of its balls in contact with the 
outside coating of a Leyden jar, and its other ball 
with the ball of the jar, the discharge will take place 
as before, but the operator, protected by the glass 
handle, receives no shock. 

If between the outside coating of a jar and one of 
the balls of the discharging rod, a piece of card- 
board is made to intervene, and the spark passed, 
the card will be found to be perforated, a burr being raised 
on both sides of it, as though two threads had been drawn 
through the hole in opposite di- Fig. 91. 
rections at the same time; and @========m€ 
from this an argument in favor 


of the theory of two fluids has 
been drawn. 

Describe the structure of the Leyden jar. How may it be used? 
Describe the discharging rod. Howis it used? What is the effect when 


When a great number of jars 
are connected together, so that 

the discharge is passed through a piece of card-board? Describe the elec- 
tric battery. 
K 


AMUN 


iy 


~~ 


il 


all their inside coatings unite, 
and all their outside coatings are 
also in contact, they constitute 
what is termed an electric bat- 
tery, as seen in Ivg.91. By this 


110 CONDENSING ACTION. 


instrument many of the more violent effects of electricity 
may be illustrated, such as the splitting of pieces of wood 
and the ignition and dispersion of metallic wires. 


LECTURE XXVII. 


EvectricaL Instruments AND Farapay’s THEORY oF 
Exectric Po.tarization.— Theory of the Leyden Jar. 
— Quadrant, Gold-leaf, and Torsion Electrometers.— 
Theory of Electric Polarization.— Specific Inductive 
Capacity. | 


Tut office which is discharged by the metallic coatings 
Fig.92. Of a Leyden jar is illustrated by the apparatus, 
1g. 92. It consists of a conical glass jar, to 
the interior and exterior of which movable coat- 
ings of thick tin plate are adapted, the interior 
one having a rod and ball projecting from it. 
This may be charged like any other Leyden vial, 
but on taking off its outside coating and remoy- 
ing its interior, they may be handled and 
brought in contact with each other, and no spark 
passes; but on restoring them to their former position, 
and applying the discharging rod, the jar is discharged. 
They therefore only serve to make a complete conducting 
communication between all parts on the interior and all 
on the exterior of the jar. 

The condensing action of the Leyden vial, which ena- 
bles it to hold so large a quantity of electricity, is due to 
induction. When the inner coating is brought in contact 
with the prime conductor, it participates in its electrical 
condition. We may therefore suppose it to be positively 
electrified. The positive electricity of the interior, de- 
composing the electric fluid of the outside coating, repels 
its positive electricity into the earth; for to charge a Ley- 
den vial the outside coating is placed in communication 
with the ground. It therefore appears that the inner coat- 
ing is positive, the outer negative, and the whole jar, view- 


What is the office of the coatings of the Leyden jar? How may this 
be proved? To what cause is the condensing action of the Leyden jar 
due? -Whatis the action of the positive electricity deposited on the inner 
coating, on the electric fluid of the outer ? 


ACTION .OF THE: LEYDEN JAR. lll 


ed together, is in the neutral condition. The interior 
coating continues, under these circumstances, to receive a 
farther charge from the prime conductor by mduction 
through the glass; this again repels more of the same 
kind, the positive, into the ground, and the negative accu- 
-mulates as before. In this manner an indefinite quantity 
might be accumulated, were it not for the fact that, owing 
to the distance which intervenes between the two coatings, 
by reason of the thickness of the glass, the quantity of 
positive electricity in the interior is never precisely neu- 
tralized by the quantity of negative on the exterior, for 
all inductive actions enfeeble as the distance increases. 

The action of the Leyden vial may be illustrated by the 
following experiments : within an Fig. 93. 
inch of the ball, a, of the prime con- Cainer COR: 
ductor, Ag. 93, bring a secondary . 
conductor, 6, supported on an insu- 
lating stem, c, and on putting the 
electrical machine in activity, two 
or three sparks will pass from a to fi ™ 
6, but after that no more. The cause of the refusal, on the 
part of the secondary conductor, to receive any farther 
charge is obviously due to the fact that the electricity 
which is already communicated to it repels that upon the 
ball, a, and prevents the passage of any more. 

If now we take a Leyden jar, 6, Fug. 94, and having 
insulated it on a stand, bring it within a 
short distance of the ball, a, of the prime 
conductor, it in the same manner will 
only receive a few sparks. But if we 
place a conductor, c, which is connected 
with the ground, near to the outside coat- 
ing, it will be found that for every spark 
that passes between a and b one passes 
between the outside coating and c, and 
the sparks follow each other in rapid suc- 
cession, until the jar becomes fully charged. From this, 
therefore, we gather, that while positive electricity is 


Fig. 94. 


Why must the outer coating be in connection with the ground? Why is 
the charge of the jar limited? What is the reason that a secondary insu- 
lated conductor refuses to receive more than two or three sparks? When 
the Leyden jar is insulated, can it be charged? On bringing a conduct- 


or in connection with the ground, near the outer coating, what is the 
result ? 


112 ELECTROMETERS. 


passing into the interior of the jar, it is escaping from the 
exterior, and that the reason the jar condenses is because 
its sides are in opposite conditions, the positive electrici- 
ty of the interior being nearly neutralized by the nega- 
tive electricity of the exterior. 

Fig. 95. Electrometers are instruments for measuring 
the intensity of electric excitement. ‘The cork 
balls, which were represented in Fug. 77, are one 
of the most simple of these contrivances. The 
distance to which they will diverge is a rough 
measure of the intensity of the electric force. 
The quadrant electrometer depends essentially 
on the same principles. It consists of an up- 
right stem of wood, Ig. 95, to which is affixed 
a semicircular piece of ivory, from the center 
' of which there hangs a light cork ball playing 
upon a pivot. When this instrument is placed on the 
prime conductor or other electrified body, the stem par- 
ticipates in the electricity, and repelling the cork ball 
which hangs in contact with it, the amount of repulsion 
may be read off on the graduated semicircle; but it is 
obvious that the number of degrees is not expressive of 
the true electrical intensity, and that no force, no matter 
what its intensity may be, can ever repel the ball beyond 
ninety degrees. 


: 


! 


fe 


The gold-leaf electrometer, Fig. 96, 
consists of a glass cylinder, a, in which 
two gold leaves are suspended from a 
conducting rod terminated by a ball or 
plate 4. On the glass opposite the leaves 
pieces of tin foil are pasted, so that when 
_ the leaves diverge fully they may dis- 
charge their electricity into the ground. 
This is a very delicate instrument for 
discovering the presence of electricity, but the torsion 
electrometer of Coulomb is to be preferred when it is re- 
quired to have exact measures of the quantity. 

Coulomb’s electrometer consists of a glass cylinder, a, 
Fig. 97, upon the top of which there is fixed a tube, 4, 
in the axis of which hangs a glass thread, 4 a, to the 


Describe the cork ball electrometer. Describe the quadrant electrome - 
ter. Why does the quadrant electrometer give inaccurate indications? De- 
acribe the gold-leaf electrometer. Describe Coulomb’s torsion electrometer 


THE TORSION ELECTROMETER. 113 


lower end of which a small bar of gum lac, c, with a 
gilt pith ball at each extremity, is fasten- 
ed. Through an aperture in the top of 
the glass cylinder, another gum lac rod, 
d, with gilt balls, may be introduced. 
This goes under the name of the carrier 
rod. 

If, now, the lower ball of the carrier 
rod be charged with the electricity to be 
measured, and introduced into the inte- 
rior of the cylinder, as seen in the figure, 
it will repel the movable ball. By taking 
hold of*the button 4, to which the upper 
end of the glass thread, a, is attached, 
we may, by twisting the glass thread for- 
cibly, bring the carrier ball and the mova- ss 
ble ballin contact. The number of degrees’ thr aivt Soto 
the thread requires to be twisted represents the amount of 
electricity. To the button, 4, an index and scale are attach- 
ed, not shown in the figure. By this we can tell the num- 
ber of degrees of twist or torsion which have been given 
to the thread. These angles of torsion are exactly pro- 
portional to the quantities of electricity. 

Many of the fundamental phenomena of electricity have 
been explained by Dr. Faraday upon the hypothesis that 
induction is an action of polarization, taking place in the 
contiguous molecules of non-conducting media, and prop- 
agated in curved lines. 

Whatever may be the form or constitution of bodies, 
an electric charge can not be given to them without at 
the same time giving a charge of the opposite kind, but 
of the samé amount, to them or other bodies in their vicini- 
ty. This charge is not confined upon their surfaces by 
the pressure of the atmosphere, but through the polariza- 
tion of the aerial or solid particles of the surrounding 
dielectrics, producing in them a charge of the same 
amount, but of an opposite kind. Thus, if a positively 
electrified ball be placed in the center of a hollow metal- 
lic sphere, the intervening space being filled with atmos- 
pheric air, the charge is not retained upon the ball by the 


What is the basis of Faraday’s theory of induction? On this theory, 
are charges confined by pressure of the air? Describe the action of an 
electrified ball in the interior of a sphere. 


K 2 


114 FARADAY’S THEORY OF POLARIZATION. 


pressure of the air, but because each aerial particle as- 
sumes by induction a polarity of the opposite kind on the 
side nearest to the ball, and of the same kind on the side 
farthest off. This state of force is therefore communica- 
ted to the interior of the hollow sphere, which is electrified 
to the same amount, but of an opposite kind to the ball. 

That this polarization of the particles takes place, is 
shown by the position which small silk fibres or spangles 
of gold assume when placed in oil of turpentine, through 
which induction is established. Each particle disturbs 
not merely that which is before it or behind it, but it is in 
an active relation with all surrounding it, aaa hence the 
polarity can be propagated in curved ee and induction 
take place round corners and behind obstacles. 

On these principles, we can easily account for the dis- 
tribution of electricity on spherical or ellipsoidal conduct- 
ors, the repulsion of bodies similarly electrified, the con-- 
densing action of the Leyden vial, and many other similar 
phenomena. 

By a variety of experiments, Dr. Faraday has proved 
that inductive action takes place in curved lines, the di- 
rections of which can be varied by the approach of bodies. 
He has also shown that the particles of solids, as gum lac, 
glass, &c., assume this character of polarity. Non-con- 
ducting bodies, through which the action of induction 

Fig. 98. takes place, are called dielectrics, and each 
of them has a specific inductive capacity. 
Thus, if three metallic plates, a 6 c, Fig. 
98, be insulated parallel to each other, at- 
mospheric air intervening between a and 4, 
and a plate of gum lac between 4 and c, the 
inductive action of the gum lac will be 
found to exceed that of the air. The fol- 
lowing table gives some of these results: 


Inductive capacity ORT a rel ote aat oe eee ne ie ee OU 
plasa rey Ses waar eas 

4 4 TAO gg 6 dpe ws un ht eh» desk SOU 

2 i BULDNUE™ os Us ante © ie reo dae oe Rie ee 


All the gases have the same inductive capacity, whatever 


Does induction take place in straight or curved lines? Can the parti- 
cles of solid bodies be polarized? What are dielectrics? What is 
meant by the specific inductive capacity of dielectrics? Of air, glass, and 
sulphur, what are the inductive capacities? What is the case with gas- 
eous bodies ? 


THE ELECTROPHORUS. 115 


their density, elasticity, temperature, or hygrometric con- 
dition may be. 

The electrophorus is an instrument which depends for 
its action on induction, and is of frequent use in chemis- 
try. It consists of a cake of gum lac or Fig. 99. 
sealing wax, 6, Fzg.99, on which is placed (} 

a flat metallic plate, a@, with an insulating 
handle, c. On exciting 6 with a piece of 
warm flannel, it becomes negatively elec- 
tric, and a being placed on it, and the 
finger brought near, a negative spark, 
driven from a by the repulsive influence of 6, is Pra. 
On lifting @ by its insulating handle, a positive spark is 
obtained; on putting it down on 6, anegative one. And 
in this manner we may obtain an unlimited number of 
sparks; positive ones when a is lifted, and negative ones 
when it is down. A little reflection will show that none 
of this electricity comes from the excited cake 8, but is. 
merely the effect of its inductive influence on the electric 
condition of the metallic plate, a. The electrophorus may 
be used when the weather is too damp for the common 
machine to work. 


LECTURE XXVIII. 


Vouitatc Evectriciry.— Of Electricity an Motion.—Sul- 
zer’s Experiment.—Galvanis Discovery. Volta’s The- 
ory— Water rs a compound Body. — Description of a 
simple Voltaic Circle and its Properties —Dvurection of 
the Current.— Different Kinds of Combinations.— Use of 
Sulphuric Acid.— Origin of the Electricity. 

Durine the last century, a German author of the name 
of Sulzer observed, that when two pieces of metal of dif- 
ferent kinds, as silver and zinc, are placed one above and 
the other beneath the tongue, as often as their projecting 
ends are brought in contact a remarkable metallic taste is 
perceived. To explain this result, he supposed that some 
kind of vibratory movement was excited in the nerves of 
the tongue. It is the first recorded phenomenon attributa- 
ble to Voltaic electricity. 


Describe the electrophorus? What fact was first described in Voltaic 
' electricity ? ¥ 


116 GALVANIC EXPERIMENTS. 


In the year 1790, Galvani, an Italian anatomist, observ- 
ed the contractions which ensue when a metallic commu- 
nication is made between the nerves and muscles of a 
dead frog; he found, that if a single metal is employed as 
the line of communication, Gontractions of the muscle take 
place whenever the metal reaches from the nerve to the 

Fig. 100. muscle ; but that if two pieces 
of different kinds are used, the 
contractions are much more 
energetic. Thus, if we take 
the skinned hind legs of a frog, 
Fig. 100, hanging together by 
a piece. éf the spine, around 
which tin foil has been twist- 
ed, every time that we simul- 
taneously touch the tin foil and 
the muscle with a bent copper wire, or with a copper and 
zinc wire, C Z, conjointly, a convulsive contraction takes 
place. 

To explain this effect, Galvani supposed that the mus- 
cular system of animals is constantly in a positively elec- 
trical state, while the nervous system is negative. In the 
same manner, therefore, that a discharge ‘takes place in 
the case of a Leyden: ‘vial, when a line of communication 
is opened between the two coatings, the muscular con- 
tractions in this case are to be accounted for. For some 
time these phenomena went under the name of animal 
electricity ; they subsequently have received the designa- 
tions of Galvanism and Voltaic electricity. 

But Volta, another Italian philosopher, was led to sup- 
pose that the cause of this remarkable result is not due to 
any peculiarity of the animal system, but to the contact 
of the pieces of metal employed. This led to the inven- 
tion of the Voltaic pile, an instrument which has achieved 
a complete revolution in chemistry. 

It is interesting to remark what great results may, in 
the hands of a true philosopher, spring from the most in- 
significant observations. ‘The convulsive spasms of a 
frog’s leg have ended in showing that the entire crust of 
the earth is made up of metallic oxides, have revealed the 


What was the fact discovered by Galvani? In what manner did he 
explain it? Under what names did these phenomena successively pass? 
What was Volta’s supposition ? 


THE SIMPLE CIRCLE. 11% 


mystery why the magnetic needle points to the north, 
and revolutionized the science of chemistry. 

What we have already said in the foregoing Lectures 
respecting electricity refers chiefly to that agent in a mo- 
tionless or stagnant state, as the mode of its distribution 
on conductors, the action of the Leyden vial, &c. The 
phenomena of Voltaic electricity are those which arise 
from electricity in a state of motion. 

From the great advances which these sciences have re- 
cently made, we are able to present the various topics in- 
volved in a much clearer way than by merely tracing 
them in a historical sketch. I shall not, therefore, pur- 
sue the order in which these facts were successively dis- 
covered, but present them in what now appears the sim- 
plest manner. 

It is to be admitted, though of that abundant proof 
will soon be given, that water is not a simple, but a com- 
pound body; that it consists of two elements, oxygen and 
hydrogen gases. It is also to be understood that metallic 
zinc may be amalgamated or united with quicksilver, by 
putting it in contact with that fluid metal, under the sur- 
face of dilute sulphuric acid. Strips of zinc thus amalga- 
mated exhibit a pure metallic brilliancy. 

If, now, we take a strip of amalgamated zinc, an inch 
wide and three or four inches long, and a piece pig. 40), 
of clean copper of similar size, z and ¢, Fig. 
101, and placing them side by side in a glass, f, 
containing water slightly acidulated with sul- 
phuric acid, we have one of the forms of a sim- 
ple Voltaic circle. In this, it is to be observed, 
that so long as the metallic plates remain with- 
out touching each other, no remarkable phe- 
nomenon appears; but if we take a metallic rod, d, and 
let it connect the top of the zinc and copper together, a 
series of new facts arises. 

First, from the surface of the copper, bubbles of gas are 
evolved; they are minute, but so numerous as to make 
the water turbid ; if collected, they are found to be hydro- 
gen gas. 


What is the difference between common and Voltaic electricity? Is 
water a simple or a compound body? What is meant by amalgamated 
zinc? Describe a simple Voltaic circle. As long as the plates are not in 
contact, does any phenomenon take place?’ On communicating by a me- 
tallic rod, what gas is evolved from the copper ? 


118 PHENOMENA OF A SIMPLE CIRCLE. 


Secondly, the plate of zinc rapidly wastes away, as is 
easily proved by weighing it from time to time; and on 
examining the liquid in the cup, we discover the cause of 
this waste, for that liquid contains oxide of zinc; coupling 
this fact with the former, we infer that, so long as the me- 
tallic rod, d, is in its place, water is decomposed, its oxy- 
genuniting with the zinc, its hydrogen escaping from the 
copper. On removing the rod, d, all these phenomena at 
once cease. 

Thirdly, if, instead of a metallic rod, d, a rod of glass, 
or other non-conductor of electricity, be employed, no de- 
composition takes place. This, therefore, indicates that 
the agent which is in operation is electricity. 

Fourthly, if for the line of communication, d, a piece 
of metal be employed, and we cautiously lift it from the 
zinc or copper plate, the moment the contact is broken, 
in a dark room we see a minute electric spark. It has 
been already observed that the electric spark can not be 
confounded with any other natural phenomenon. 

Fifthly, if the line of communication be a very slender 
platinum wire, as long as it remains in its position, its tem- 
perature rises so high that it becomes red hot, and may be 
kept so for hours together. Now, recollecting that the 
ignition and fusion of metals take place when they are 
made to intervene between the coatings of a Leyden_vial, 
and considering all the facts which have just been set 
forth, we see that the following conclusion may be drawn: 
that in an active simple Voltaic circle water is decom- 
posed, its oxygen going to the zinc and its hydrogen to 
the copper, and that a continuous current of electricity 
accompanies this decomposition, running from one metal 
to the other, through the connecting rod. 

The direction of this current may be determined by 
several processes; it is as follows: the electricity, leaving 
the surface of the zinc, passes through the liquid to the 
copper, then moves through the connecting wire back 
again to the zinc, performing a complete circuit; hence 
the term Voltaic circle. 

Simple Voltaic circles are of several kinds; that which 


What happens to the zinc? Why do we infer that water is decom- 
posed? Ifa glass rod is used instead of a metallic one, what is the result? 
How can a spark be made visible? Can a platinum wire be ignited? 
From these facts, what conclusions may be drawn? What is the course 
of the current? 


5 
ELECTROMOTIVE SOURCE. 119 


we have been considering consists of two different metals 
with one intervening liquid, but similar results can be ob- 
tained with one piece of metal and two different liquids. 

In the foregoing experiment, we have used dilute sul- 
phuric acid: this acid discharges a subsidiary duty. Zinc, 
when it oxidizes, is covered with a coating impermeable 
to water and air; it is this grayish oxide which protects 
the common sheet zinc of commerce from farther change. 
When, therefore, a Voltaic pair gives rise to a current by 
the oxidation of its zinc, that current would speedily stop 
were not the oxide removed as fast as it forms; this is 
done by the sulphuric acid, which forms with it a sul- 
phate of zinc, a substance very soluble in water, and the 
metal thus continually presents a clear surface to the water. 

As to the immediate cause which gives rise to the Vol- 
taic current, there has been a difference of opinion among 
chemical authors. Volta believed that the mere contact 
of the metals was the electromotive source, and endeay- 
ored to prove, by direct experiment, that if a piece of 
copper and zinc are brought in contact and then sepa- 
rated, they become excited, the one positively, and the 
other negatively; upon these principles, he was led to the 
discovery of the Voltaic battery. But many facts have 
now indisputably shown that the origin of the current is 
to be sought in the chemical changes going on; and in 
the instance we have had under consideration, it is due 
to the decomposition of water. That the electromotive 
action does not depend on the contact of the metals, seems 
to be proved by the fact that, by changing the nature of 
the liquid intervening between them, we can change the 
current both in direction and force. 

What other kinds of Voltaic circles are there? What is the use of 
sulphuric acid in these combinations? What was Volta’s opinion as to 


the electromotive source? What is the view now taken? What argu- 
ments may be adduced for its correctness ? 


120 THE VOLTAIC PILE. 


LECTURE XXIX. 


Errects or Vouiraic Evectriciry.—Invention of the Vol- 
taic Pile—Cruickshank’s Trough—Hare’s Battery.— 
Smee’s Simple and Compound Battery.—Grove’s Batte- 
ry.— Voltaic Effects, the Spark, Deflagration of Metals. 
—ILIgnition of Wires.—Arc of Flame.— Decomposition 
of Water.— Nature of the Gases evolved. 


Ir has been already observed that, in the discussions 
which arose respecting animal electricity, Volta attributed 
the action entirely to the metals employed ; and reasoning 
on this principle, he concluded that the effect ought to in- 
crease, if, instead of using a single pair of metals, a great 
number of alternations were employed. Accordingly, on 
taking thirty or forty silver coins and discs of zinc, and 
pieces of cloth moistened with acidulated water, of the 

Fig. 102. same size, and arranging them in a pile or 
column, carefully observing to place them in 
the same order, silver, cloth, zinc—-silver, 
cloth, zinc, &c., he found his expectation ver- 
ified. On touching, with moistened hands, 
the ends of the pile, a shock was at once re- 
ceived, and on making them communicate 
by a piece of wire, an electric spark passed. This instru- 
ment, fg.102, is the Voltaic pile. 

From the important uses to which the pile was soon 
devoted, it became necessary to have it under a more con- 
venient form. There are several inconveniences attend- 
ing the original construction: it is lable to overset, is 
troublesome to put in action, and requires to be taken to 
pieces and carefully cleaned every time it is used ; its 
maximum effect lasts but a short time, owing to the weight 
of the superincumbent column pressing out the moisture 
from the lower pieces of cloth; and as soon as they become 
dry, all action ceases. 

These difficulties were avoided, to a great extent, in the 
trough battery, which soon replaced the former instru- 
ment. It consists of a box, or trough, vg. 103, three or 


How was Volta led to the invention of the pile? Describe the Voltaic 
pile? What are its effects? What inconveniences are there in the 
original form ? 


CRUIKSHANK’S, HARE’S, AND DANIELL’S BATTERIES. 121 


four inches square at 
the ends, and a foot or 
more long; grooves 
are made in thesides f, Woo 
and bottom of this HP bs on eer 
box, and into them (=ssmsss================= 
pieces ofzinc and cop- <= 
per, soldered face to face, are fastened, water tight, by 
cement. These grooves are about half an inch apart, and 
into their interstices acidulated water is poured, care be- 
ing taken that the metals are arranged in the same direc- 
tion, so that if the series begins with a copper plate it 
ends with a zinc. The apparatus is obviously equivalent 
to Volta’s pile laid on its side, and the facility for charg- 
ing it, and removing the acid when the experiments are 
over, is very great. From the extremities two flexible 
copper wires pass; they are called the polar wires, or elec- 
trodes of the battery. 

Some very convenient forms of Voltaic battery have 
been invented by Dr. Hare. In one of these, the liquid 
is poured off and on the plates by a quarter revolution of 
a handle; in others, the trough is made movable, so that 
it lifts up when all the arrangements are ready, and the 
plates are immersed. 

When it is required to have a current, the py». 104, 
intensity of which remains constant for a length 
of time, Daniell’s battery is to be preferred. 
It consists of a copper cylinder, C, Fig. 104, 
in which a solution of sulphate of copper is 
poured; within this is a second cylinder, P, of ___4 : 
porous earthen-ware, filled with dilute sul- = Tt 
phuric acid, A, into which an amalgamated [=i 
zinc rod, Z, dips. From the copper and zinc, 
rods project, terminated by binding screws, 
with which the polar wires may be connected. 

Smee’s battery is also a very valuable com- | E 
bination; it consists of a plate of platinized La 
silver, or platinized platinum, 8S, Fig. 105, on each sid 
of which are placed parallel plates of amalgamated zinc, 
Z; these plates are held tightly against a piece of wood, 


tH 


Describe the trough battery. Describe some of the improvements in 
the battery. What are the forms introduced by Hare, Daniell, Smee, and 
Grove respectively ? 

L 


122 SMEE’S AND GROVE’S BATTERIES. 


w, by means of a clamp, 6, to which, and 
also to the silver plate, binding screws, 
for the purpose of fastening polar wires, 
are affixed. ‘The whole is suspended, 
by means of a cross piece of wood, in a 
jar containing dilute sulphuric acid. 

Smee’s compound battery, represent- 
ed in Fxg. 106, is nothing more than a 
series of the foregoing simple circles. 
The figure shows one containing six 
ll — cells; the position of the platinized sil- 
“=~ ver and zinc plates of one of the pairs 
is seen at S and Z. It is to be charged 
with dilute sulphuric acid. 


Fig. 106. 


yA nm TTT — = d 
Ah Ae ip pe Cp a 
4 | | elel4 ar 


Probably the most powerful of all Voltaic combina- 
tions is the instrument invented by Mr. Grove. 
It consists of two metals and two liquids, amal- 
gamated zinc and platina, dilute sulphuric acid 
and strong nitricacid. A jar, P, Fig. 107, three 
quarters of an inch in diameter, and made of 
porous or unglazed earthen-ware, is to be filled 
with strong nitric acid, N, and in ita slip of pla- 
tina is placed; this porous earthen-ware cup is 
then set in a glass cup, A, nearly three inches in 
diameter ; in this is placed a plate of zinc, Z, one 
eighth of an inch thick, and of such a size, as 
respects its other dimensions, that it will readily 
pass between the porous cup, P, and the glass. 
In the glass, A, is placed dilute sulphuric acid. 

In this manner several cups are to be provided, the ar- 
rangement being, zinc in contact with dilute sulphuric 
acid, and platina in contact with strong nitric acid, with a 
porous cup intervening between. The workman also 


> Se 


DEFLAGRATION OF METALS. 123 


previously connects each zinc cylinder with the slip ot 
platina, which is in the next cup, by soldering between 
them a strip of copper. 

Grove’s battery owes its force to the decomposition of 
water by zinc. But the hydrogen is not evolved from the 
surface of the platina, as it would be in a single circle ; 
it is here taken up by the nitric acid, which undergoes 
rapid deoxidation, and therefore, during the use of this 
battery, volumes of deutoxide of nitrogen are evolved. 
A battery of fifty cups gives rise to very striking effects ; 
but five or ten are quite sufficient to repeat all the follow- 
ing experiments. « 

On separating the polar wires of such a battery from 
each other, a brilliant spark passes, and, if the separation 
be gradual, a flame constantly «proceeds from one to the 
other; the light of which, when the wires are of copper, 
is of a beautiful green color. 

If, on the surface of some quicksilver Fig. 108. 
contained in a glass, Fug. 108, we low- 
er a thin piece of steel, or iron wire, 
connected with one of the poles of the 
battery, the mercury being kept in con- 
tact with the other, the steel takes fire 
and deflagrates beautifully, emitting 
bright sparks, and the mercury is rap- 
idly volatilized. | 

‘When thin metal leaves are made to intervene between 
the polar wires, they are at once dissipated, the flames 
they emit being of different colors in the case of different 
metals. 

If a piece of platinum wire is made the channel of 
communication from one pole to the other, if it does not 
fuse at once, it becomes incandescent, and remains so as 
long as the instrument is in activity. 

When the polar wires are terminated by pieces of well- 
burned charcoal, or that variety of carbon which is formed 
in the interior of gas retorts, the light which passes between 
them when they are removed from contact is one of the 


What are the chemical effects taking place in Grove’s battery? On 
separating the polar wires of a battery, what phenomenon arises? How 
may iron wiré be deflagrated? What phenomenon is seen during the 
deflagration of metallicleaves ? When a thin platinum wire communicates 


between the ” sa what is the result? How is the arc of light formed, 
and what areits properties ? 


5 


124 DECOMPOSITION OF WATER. 


most brilliant that can be obtained by any artificial means. 
With powerful batteries, the pieces of charcoal may be sep- 
Fig. 109. arated several inches apart without the 
x light ceasing, and then it moves from 
. : one to the other pole in an arched form, 
Fig.#109, the convexity of the arc being upward. This 
form is due to the current of hot air which rises from the 
ignited space between the poles, and the light may be 
blown out by the mouth, just in the same manner that we 
blow out a candle. 
But, in a scientific point of view, by far the most inter- 
esting experiment to be made with the Voltaic battery is 
Fig. 110. the decomposition of water. Through 
the bottom of a glass vase, or dish, at 
the point a 6, Fig. 110, two platinum 
wires are introduced, water-tight ; they 
pass into the vase, as a c, 6 d, parallel 
to each other, but not touching. Over 
each of these wires a tube is to be in- 
verted ; the tube e over c, and fover d, 
the vase and the tubes being previous- 
ly filled with water acidulated slightly, to improve its 
conducting power. Now let the wire a c be connected 
with the positive pole of the Voltaic battery, and é d with 
the negative; bubbles of gas in a torrent arise from their 
extremities, and pass upward in the tubes, displacing the 
water. The quantity of gas thus collecting in the two 
tubes is unequal, and whenever we stop the decomposi- 
tion there will be found inf double the quantity which is 
ine. When a sufficient amount is collected, let the tube 
e, containing the smaller portion of gas, be cautiously re- 
moved, preventing any atmospheric air from getting into 
its interior, by closing it with the finger, and then, turning 
the tube upside down, let a stick of wood, with a spark 
of fire on its extremity, be immersed in the gas. In a 
moment the wood bursts into a flame, proving that this is 
oxygen gas. Then take the other tube, and allow to pass 
into it a quantity of atmospheric air equal to the volume 
of gas it already holds; remove the finger and apply a 
light, and there is an explosion. But this is the property 


Describe the process for the decomposition of water. What is the rel- 
ative proportion of the gases collected? How can it be proved that the 
less quantity is oxygen and the larger hydrogen? ‘ : 


POLAR DECOMPOSITION. 125 


_of hydrogen gas. We therefore conclude that in this ex- 
periment water has been decomposed and resolved into 
its constituent ingredients, oxygen and hydrogen; and, 
farther, that in water there is, by vol- - pig. ayy, 
ume,twice as much hydrogen as there ¢ 

is oxygen gas. The separation of the 
two is perfect, so much so that the de- 
composition may be conducted in differ- 
ent vessels. Thus, let N and P be tubes, 
through the closed upper ends of which 
platinum wires pass; invert them in 
glasses of water, with a siphon of large 
bore connecting them. On making N 
communicate with the negative, and P with the positive 
pole, decomposition ensues, hydrogen gas accumulating in 


N, and oxygen in P. 


LECTURE XXX. 


Tue Evecrro-cuemicat Turory.— Theory of the Decom- 
position of Water.—Decomposition of Metallic and other 
Salts —Becquerel’s Illustration of the Formation of Min- 
erals —Davy’s Discoveries —Electro-chemical Theory.— 
Electrolytes—Faraday’s Theory of definite Action — 
The Electrotype. 

® 


THE prominent fact connected with the decomposition 
of water is the total separation of the constituent elements 
on the opposite polar wires or electrodes. From the 
positive wire oxygen alone escapes, and from the nega- 
tive hydrogen; there is no partial admixture, but the 
separation is perfect and complete. 

Though the polar wires may be separated from each 
other by a considerable distance, the same result is uni- 
formly obtained, and it is to be remarked that the evolu- 
tion of gas takes place on the wires alone ; no intervening 
bubbles make their appearance in the intermediate space. 
The principle on which this is effected may be easily under- 


What is the constitution of water by volume? Do these polar decom- 
positions effect a total separation of the bodies? In the decomposition of 
water, do any gas bubbles appear in the intervening space ? 


126 VOLTAIC DECOMPOSITIONS. 


stood, by supposing H H and O O, Fig. 112, to represent 


Fig. 112. atoms of hydrogen and oxygen respect- 

O 0 ively; each pair of them, therefore, rep- 
eeeaee resents a particle of water. Now, if we 
; , slide the upper row of atoms upon the 
ACH lower, as shown at 4 h, 0 0, it is obvious 


that a hydrogen atom will be set free at 
one extremity of the line, and an oxygen atom at the oth- 
er, and that, as respects all the intermediate pairs of atoms, 
though they have changed their places, yet every particle 
of hydrogen is still associated with a particle of oxygen, 
constituting, therefore, a particle of water; and it is at the 
extremes of the line alone that the gases are set free. So 
in the polar decomposition by the pile, all the liquid in- 
tervening between the poles is affected, decompositions 
and recombinations successively taking place, the hydro- 
gen atoms moving in one direction, the oxygen in the 
other, finally to be set free on the surface of the polar 
wires. 

This capital discovery of the decomposition of water 
by Voltaic electricity was originally made by Nicholson 
and Carlyle. It is by far the most satisfactory method ot 
demonstrating the constitution of that liquid. After it 
was made known, any lingering doubts which still remain- 
ed on the minds of some chemists in relation to the com- 
posite nature of water were speedily removed. 

In the same manner that water is decomposed by the 
Voltaic battery, so, also, many metallic and other salts yield 
to its influence. ‘Thus, if into a jar containing a solution 
of blue vitriol, the sulphate of copper, two metallic plates 
are introduced parallel to each other, and one of them 
brought in connection with the negative and the other 
with the positive pole of the battery, decomposition of the 
salt takes place; the sulphate of copper being resolved 
into its constituents, sulphuric acid and the oxide of cop- 
per, and the latter reduced to the condition of metallic 
copper by hydrogen simultaneously evolved with it, arising 
from the decomposition of a part of the water. In this 
manner the copper may be deposited, with a little care, 
under the form of a tough metallic mass. 


How is this explained? How is it, if decompositions are going on in the 
intervening space, that the gases are not there seen? Can metallic salts 
be in like manner decomposed ? 


BECQUEREL’S EXPERIMENTS. 127 


Ifin a cubical glass vessel Fg. 113, divided into two par- 
titions by a diaphragm, a, Fig. 113. 
and both partitions filled 
with a solution of iodide 
of potassium, mixed with 
a solution-of starch, and 
the positive and negative « 
wires of the battery intro- 27 
duced, decomposition of the iodide takes place, its iodine 
being evolved at the positive wire, and giving with the 
starch a deep blue color, the blue iodide of starch, while 
the liquid in the other partition remains colorless. 

M. Becquerel obtained some very beautiful results by 
the aid of weak but long-continued electric currents, illus- 
trating the probable mode of formation of mineral sub- 
stances by such currents traversing the crust of the earth. 
If we take a glass tube bent into the form Fig. 114. 
of a U, and close the bended part with a 
plug of plaster of Paris, putting in one of 
the branches a solution of carbonate of 
soda, and in the other of sulphate of cop- 
per, immersing in one of the solutions a 
zinc plate, and in the other a copper, 
connected together by a piece of bent 
wire, the liquids communicate through 
the porous plug, and crystals of the dou- 
ble carbonate of copper and soda form on the plate im- 
mersed in the copper liquid. In the same © Fig. 115. 
manner, other compound salts and mineral mu 
bodies may be produced. 

Or if we take a jar, A, and fillit with a so-» -e. = 
lution of nitrate of copper to a, and then with -ysiilli#) 
dilute nitric acid to B, and immerse in it a slip 
of copper, C D, presenting equal surfaces to 


Describe the polar decomposition of iodide of potassium. Can decom- 
positions be produced by very feeble Voltaic currents? Describe some 
of the arrangements of M. Becquerel for illustrating the probable mode of 
formation of minerals. 


128 ELECTRO-CHEMICAL THEORY. 


dergo decomposition by the action of the pile, it occurred 
to Sir H. Davy that probably other substances, at that time 
supposed to be simple, might also be decomposed. He 
accordingly subjected the alkaline and earthy bodies, then 
reputed to be elementary, to the influence of a powerful 
battery, and found that his supposition was verified. On 
placing a fragment of caustic potash between the poles, it 
immediately melted; from the positive oxygen gas es- 
caped in bubbles, and from the negative, small metallic 
globules, having the appearance of quicksilver, emerged; 
these were characterized, however, by the singular qual- 
ities of an intense affinity for oxygen, so that they would 
take fire on being touched by water, or even ice, and 
-were so light as to swim upon the surface of that liquid. 

The result of Davy’s experiments proved that the al- 
kaline substances and all the earths are oxidized bodies, 
and in most instances oxides of metals. 

On these principles, Davy established a division of ele- 
mentary bodies into electro-positive and electro-negative 
substances. The former are those which, during a polar 
decomposition, go to the negative pole, and the latter those 
that go to the positive. The electro-chemical theory as- 
sumes that all bodies have a natural appetency for the as- 
sumption of the positive or negative states respectively, and 
that all the phenomena of chemical combination are mere- 
ly cases of the operation of the common law of electrical 
attraction ; for between particles in opposite states at- 
traction ought to take place, and when in a compound 
body, such as water, which consists of particles of nega- 
tive oxygen and positive hydrogen, the poles of an active 
Voltaic battery are immersed, they will effect its decom- 
position, the negative oxygen going to the positive pole 
and the positive hydrogen to the negative pole. 

Davy’s theory thus not only accounts for the decom- 
posing agencies of the battery, but also for all common 
cases of chemical combination, referring both to the fun- 
damental law of electric attraction. With all its simplic- , 
ity, it would be very easy to show, however, that it is 
founded on a groundless assumption, and can not account 
for a great number of well-known facts. 


‘What were the discoveries of Davy respecting the alkaline and earthy 
bodies? What is meant by the electro-chemical theory? Does this the- 
ory also account for chemical combination ? 


he 


THE ELECTROTYPE. 129 


The Voltaic pile can not decompose all bodies indis: 
criminately. An electrolyte—for so a decomposable sub- 
stance is termed—must always be a fluid body. It also 
appears that all electrolytes must have a binary constitu- 
tion, or contain one atom of each of their two constituent 
ingredients. ’ 

Mr. Faraday discovered that the action of an electric 
current in effecting the decomposition of various bodies is 
perfectly definite: thus, if we make the same current 
pass through a series of vessels containing water, iodide 
of potassium, melted chloride of lead, they will all be de- 
composed, but in very different quantities. If of the wa- 
ter there be decomposed 9 parts, there will be 165 of 
iodide of potassium, and 139 of chloride of lead; but 
these numbers represent what will be hereafter given as 
the atomic weights of the bodies in question. <A current 
which can set free one grain of hydrogen will evolve 108 
of silver, 104 of lead, 39 of potassium, 31°6 of copper, &c., 
these being the atomic weights of those substances respect- 
ively. 

A very beautiful application of electro-chemical decom- 
position has, of late, been introduced into the arts. It 
passes under the name of the electrotype. It consists in 
the precipitation of metallic copper, gold, silver, platina, 
&c., on different surfaces, by the aid of a Voltaic current. 
Thus, suppose it were required to obtain a perfect copy 
in copper of one of the faces of =~ Fig. 116. 

a medal; let a glass trough, 
N C, Fig. 116, be filled with 
a solution of the sulphate of 
copper, and to the negative 
wire, Z, of a Smee’s Voltaic 
battery, let the medal N be at- 
tached, all those portions, ex- 
cept the face designed to be 
copied, being varnished over, [/ 
or covered with wax, to pro- “ : 

tect them from contact with the liquid. To the positive 
wire, S, let there be attached a mass of copper, C. As 
soon as the battery is in action, decomposition of the sul- 


To what bodies is the decomposing influence of the Voltaic battery lim- 
ited? Can substances other than binary compounds be thus decomposed ? 
Explain Faraday’s law of the definite action of a Voltaic current. De. _ 
scribe the electrotype. 


130 THE VOLTAMETER. 


phate takes place, metallic copper is precipitated on the 
face of the medal, copying it with surprising accuracy. 
This copper is, of course, withdrawn from the sulphate 
in the solution ; but while this is going on, sulphuric acid 
and oxygen are being evolved on the mass of copper, C. 
They therefore unite with it; and thus, as fast as copper 
is precipitated on N by oxydation, new quantities are ob- 
tained from C, and the liquid keeps up its strength unim- 
paired. In the course of a day the medal may be re- 
moved. It will be found incrusted with a tough, red 
coat of copper, which may be readily split off from it. It 
is a perfect copy of the surface on which the deposition 
took place, and, in turn, it may be used as a mould for 
obtaining a great number of casts. Gilding, silver- 
plating, and platinizing are now performed on the same 
principles, the electrotype being one of the most beauti- 
ful contributions which science has of late given to the 
arts. 
Aw instrument, the Voltameter, has been invented by 
Fig. 117. Mr. Faraday for measuring quantities of 
Voltaic electricity. It is represented in 
Fig. 117. It consists of a glass jar, 4, 
filled to the height d with water, and 
through its cover, c, a graduated tube, a, 
passes. In the lower part of the tube at 
g, two pieces of platina foil, which form 
the terminations of the polar wires of the 
battery, the current of which is to be 
measured, are introduced, the connection 
with those wires being made by the aid of 
the mercury cups,ef. The tube, a, having 
= been filled with water, as soon as the cur- 
rent passes decomposition takes place, the 
gases collecting in the graduated tube, and measuring 
the amount of the current. 


Describe the Voltameter. 


DIFFERENT VOLTAIC BATTERIES. 13l 


LECTURE XXXI. 


Oum’s Turory or THE VottTaAic Pite.—MAGNETISM AND 
ELecTRO-MAGNETISM.—Volta’s Pile-—Hare’s Calorimo- 
tor—Zamboni’s Pile-—Ohm’s Theory.—LElectro-motive 
Force.—Resistance.—General Law for the Force of the 
Current.—Laws and Phenomena of Magnetism.—Elec- 
tro-magnetism, Oersted’s Discoveries in—The Galvan- 
ometer.—Llectric Rotations.— Tangential Force —Elec- 
tro-magnets. 


Wir a given amount of metallic surface we can pro- 
duce Voltaic batteries having different qualities. Thus, 
if we take a square foot of copper and a square foot of 
zine, and place between them a piece of wet cloth, we 
shall have a battery which can not give shocks, nor effect 
the decomposition of water, but which will cause a fine 
metallic wire to become cake hot, or even to fuse. If, 
again, we take a square foot of copper and a square foot 
of zinc, and cut each into 144 plates, an inch square, and 
arrange them with similar pieces of cloth as a Voltaic 
pile, the instrument will give sho k ,and decompose wa- 
ter rapidly. From the same quantity of metal two differ- 
ent species of battery may be made; one consisting of a 
few plates of large surface, or one of a great number of 
alternations of smaller plates. | 

Of these varieties of battery, the calorimotor of Dr. 
Hare is an example of the first. It consists of a series 
of zinc plates, all connected together, and one of copper, 
also similarly connected, constituting therefore, in reality, 
a single pair of very large surface. The great amount of 
heat evolved by this apparatus is its peculiarity. 

The electric pile of Zamboni is an example of the other 
kind. It consists of a series of ten or twenty thousand 
dises of gilt paper, alternating with similar pieces of 
very thin zinc foil. These are arranged in a tube, and 
kept in contact by the pressure of screws at each end. 
In Fig. 118 (p. 132), the pile is laid on a pair of gold 


What are the two principal forms of battery? What do the calorimo- 
tor and Zamboni’s pile illustrate? What is the effect produced by a bat 
tery of large plates? What by one of many alternations ? 


132 OHM’S THEORY OF VOLTAIC CURRENTS. 


re M8. * «leaf electroscopes, both of 

ie which diverge,- the one 
being positive and the 
other negative, the cen- 
tral parts of the pile being 
neutral. This instrument 
exhibits no calorific ef- 
fects; its phenomena are 
those of electricity of high 
tension. 

These, and, indeed, 

= many of the phenomena 
of the electric current, are clearly accounted for by the 
aid of Ohm’s theory of the Voltaic pile, of which the fol- 
lowing is an exposition : 

1st. By ELECTRO-MOTIVE FORCE we understand the 
causes which give rise to the electric current; this, as 
we have explained in the simple circle, is the oxidation 
of the zinc. 2d. By resistance we mean the obstacles 
which the current has to encounter in the bodies through 
which it passes. 

When we affect the electric current in any portion of 
its path, either by varying the electro-motive force, or 
changing the resistances, we simultaneously affect it 
throughout the whole circuit; so that, in a given space 
of time, the same quantity of electricity passes through 
each transverse section of the circuit. 

In any Voltaic circle, simple or compound, the force of 
the current is directly proportional to the sum of all the 
electro-motive forces which are in activity, and inversely 
proportional to the sum of all the resistances; that is to 
say, the force of any Voltaic current is equal to the sum 
of all the electro-motive forces; divided by the sum of all 
the resistances. 

The resistance to conduction of a metal wire is directly 
as its length, and inversely as its section; that is to say, 
the longer the wire is, the greater its resistance, and the 
thicker it is, the .ess its resistance. 

If we augment or diminish, in the same proportion, the 


What is meant by electro-motive force? In a simple circle, what is its 
origin? Whatis meant by resistance? On affecting one part of a cur- 
rent, is the rest affected? What conclusion is drawn from that fact? 
What is the force of the cwrent equal to? In a wire, what is the law of 
resistance ? 


OHM’S THEORY. ~ 133 


electro-motive forces and the resistances of a Voltaic cir- 
cuit, the force of the current will remain the same; if we 
increase the electro-motive force, the force of the current 
increases; if we increase the resistance, the force of the 
current diminishes. 

If, in two Voltaic circles of equal force, the same re- 
sistance is introduced, the forces of the currents may be 
enfeebled in very different proportions ; for the newly-in- 
troduced resistance may, in one of the circles, bear a very 
great proportion to the resistances already existing, and, 
in the other, a very insignificant proportion. 

The following, therefore, is the general law which de- 
termines the force of a Voltaic circuit. 

1st. The electro-motive force varies with the number of 
the elements, the nature of the metals, and of the liquids 
which constitute each element; but it does not in any 
manner depend on the dimensions of their parts. 

2d. The resistance of each element of a Voltaic circuit 
is directly proportional to the distance between the plates, 
as occupied by the liquid, the resistance of the liquid it- 
self, and the length of the polar wire connecting the ends 
of the circuit; and inversely proportional to the surface of 
the plates in contact with the liquid, and to the section of 
the connecting wire. 

3d. The force of the current is equal to the electro- 
motive force divided by the resistance. 

From the circumstance that lightning has been repeat- 
edly known to render implements of steel magnetic, and 
from a general analogy which exists between the phenom- 
ena of magnetism and those of electricity, it was long ago 
believed that these phenomena were due to one common 
cause; but it was not until 1819 that their true relation- 
ship was first established by Cirsted. 

The phenomena ofthe magnet itself were discovered 
more than 2000 years ago. ‘he natural magnet, or load- 
stone, which is an iron ore, possesses the quality of at- 
tracting pieces of iron or steel, but upon almost all other 
substances it is without action. To hardened steel it com- 


How does the force of the current change with changes in the electro- 
motive force and the resistance? When a new resistance is introduced 
into two circles, does it follow that both will be affected alike? Give the 
general law which determines the force of the Voltaic current. What are 
the properties of a magnet? hat is the difference of its action on iron 
and steel? 

M 


134 MAGNETISM. 


municates its own properties in a permanent manner ; but 
soft iron is only transiently magnetic, and as soon as it is 
removed from the influence of the magnet it loses its 
power. Bars of steel which have been magnetized can 
communicate their activity to other bars; they are, there- 
fore, of constant use in physical investigations, and are of 
two forms, straight bars and horseshoe magnets. 
Fig. 119. If a magnetic bar have iron 
ioe, filings sifted over it, they col- 
lect, as represented in Fig. 
wim | * 119, chiefly at the two extrem- 
ities, d d, few of them being found in the middle. Ifa | plece 
Fig. 120. of card-board is laid 
a h 4 over a magnet, and 
the filings dusted on 
it, they arrange them- 
| selves in curves, call- 
7 ed magnetic curves ; 
there being in this, 
as in the former in- 
= stance, centers of ac- 
<y tion, P P, toward the 
“extremities of the 
bars, around which the curves are arranged. The ap- 
pearance is shown in Fg. 120. 
A light magnetic bar,S N so arranged that it can be pois- 
Fig. 121. ed on a pivot, C, with free- 
C dom of motion, is a magnetic 
N needle. It was discovered 
by the Chinese that such a 
needle, Fig. 121, possesses 
polarity, or points north and 
south, a fact of the utmost 
importance in navigation. 
When to a needle the poles 
of a bar are ptisitiod it exhibits attractive and repuls- 
ive movements. ‘The law under which these take place 
is, “ Like poles repel, and unlike ones attract ;” two north 
or two south poles repel, but a north and a south attract. 


2 
Cie 
7 dun heey 
oO TTR 


What are the forms of artificial magnets? How may the existence of 
poles be shown by iron filings? Describe a magnetic needle. What is 
meant by its polarity? What is the law of magnetic attractions and re- 
pulsions 7 


ELECTRO-MAGNETISM. 135 


Hither pole of a magnet is attracted by a piece of unmag- 
netized soft iron. The intensity of magnetic action is in- 
versely proportional to the square of the distances. 

If a magnetic needle be brought into the neighborhood 
of a wire, along which an electric current is passing, the 
needle is at once disturbed from its position, and tends to 
set itself at right angles to the wire. The direction in 
which the transverse movement takes place depends on 
the relative position of the needle and the wire ; thus, Ist, 
if the wire be above the needle and parallel to it, that 
pole next the negative end of the battery moves west- 
ward; 2d, if the wire be beneath the needle, it will move 
eastward ; 3d,if the wire be on the east side of the needle, 
the pole is elevated ; 4th, if on the west, it is depressed ; 
in all these various positions, the tendency being to bring 
the needle at right angles, or transverse to the wire. 

It follows, from these Fig. 122. 
facts, that if a magnet- 


ic needle be placed in 
the interior of a rectan- 
gle of wire, Fig. 122, 
through which a cur- 
rent is made to flow, 
all the portions of the 
wire conspire to move 
the needle in the same direction. The effect, therefore. 
becomes much greater than in the case of a single con- 
tinuous wire. 

On the same principle, if, instead of a single turn, the 


hee is repeatedly coiled upon it- Fig. 123. ° 


self, so as to make a great many 
turns, the effect upon the needle may | 
be greatly increased; and when the 

» needle is made nearly astatic, that 
is to say, its tendency to point ‘north 
nearly destroyed by arranging it upon 

an axis with another needle, similar to it in all respects, 

but with its poles reversed, as N 8,5 N, Fegure 123, 

the directive tendency of the one needle neutralizing 


How does the intensity of magnetic action vary? In what does @r- 
sted’s discovery consist ? What is the direction which the needle moves 
in the four positions round the wire? What is the effect on a needle in 
the interior of a rectangle? What is the principle of the galvanometer ? 


136 ELECTRO-MAGNETIC ROTATION. 


the other, but both tending to turn in the same direction 
by the current in the coil of wire, inasmuch as one is with- 
in the coil and the other above it, the arrangement forms 
a most delicate means of discovering and measuring an 
electric current. It is called a galyanometer. 

As action and reaction are always equal and contrary, 
it is obvious that, if a conducting wire be movable and 
the magnet stationary, the latter can be made to impress 
motions on the former. 

Conducting wires can be made to revolve round the 

Fig. 124. poles of a magnet, or the pole of a mag- 
net round a conducting wire; thus, in a 
glass cup, Fug. 124, let a magnet, m, be 
fixed vertically, and the cup filled with 
mercury; by means of a loop, a, let a 
conducting wire, 6, be suspended, having 
perfect freedom of motion. Ifan electric 
current is made to pass down this wire 
through the mercury, and escape by the 
path d, the wire rotates round the pole 2 
as long as the current passes. From this 
and similar experiments, it therefore ap- 
pears that the force exerted between a conducting wire 
and a magnet is not a direct attractive or repulsive power, 
but one continually tending to turn the movable body 
round the stationary one, deflecting it continually, and 
acting in a tangential direction. Hence it is sometimes 
spoken of as a tangential force. 

If round a bar of soft iron a conducting wire, covered 

Fig. 125. over with silk, be spirally twisted, as 1 
Fig. 125, whenever an electric current 
is passed, the iron becomes intensely 
magnetic, and loses its magnetism as 
soon as the current stops. A bar an 
inch in diameter, bent so as to represent 
a horseshoe, Fwg. 126, with a wire cov- 
ered with silk for the purpose of sepa- 
rating its successive strands from each 


On the same principles, can the wire be made to move? Describe a 
method of showing the rotation of a wire round the pole of a magnet. 
What is the nature of the force exerted between a conducting wire and 
amagnet? Describe the construction and properties of a straight electro- 
magnet. <a 


r*. 


ELECTRO-MAGNETS. 137 


other, may be made to give rise to very Fig. 126 
striking results. Prof. Henry, by a modi- rTP 
fication of the conducting wire, succeeded 
in imparting so intense a degree of mag- 
netism to a piece of soft iron that it could § 
support more than aton weight. If under } 
one of these ELECTRO-MAGNETS a dishful of 
small iron nails be held, the moment the 
current passes, the nails are all attracted, 
and, while they are held by its poles, may 
be moulded, as it were, by the hand in 
various shapes, but as soon as the current 
stops they fall off. 

It is upon this principle of producing 
temporary magnetism by an electric cur- 
rent that Morse’s electric telegraph depends. 


LECTURE XXXII. 


ELECTRO-DYNAMICS — THERMO-ELECTRICITY, &c.— Am- 
pere’s Discovery.— Properties of a Helix. Nature of the 
Magnet — Faraday’s Discovery of Magnetic Electricity. 
—Magnetic Machines—Faradian Currents.— Thermo- 
electricity.— Production of Heat and Cold by Electric 
Currents— Thermo-electric Pairs —Peculiarity of these 
Currents. — Electro-motive Power of Heat.— Melloni’s 
Pile and Thermometer.—Improvements in Thermo-elec- 
tric Pairs —Animal Electricity— Steam Electricity. 


Soon after the relation between electricity and magnet- 
ism was established, M. Ampere discovered that there 
are reactions between electric currents themselves. 

Two electric currents flowing in the same direction at- 
tract each other, but two electric currents flowing in op- 
posite directions repel; or, more briefly, ‘“ Like currents 
attract, and unlike ones repel.” 

If a conducting wire be bent in the form of a helix, 
its terminations returning toward its middle, as shown in 
fig. 127, it exhibits all the properties of an ordinary mag- 
netized bar; for as soon as the current passes, it points 


Describe the horseshoe electro-magnet. What is the law of reaction 
between electric currents ? 
M 2 


138 PROPERTIES OF A HELIX. 


Fig. 197. north and south, and is attracted and re- 
pelled by the poles of a magnet, just as 
though it were a magnet itself. A very 
neat arrangement for illustrating these 
results is seen in vg. 128. A small sim- 
ple circle, consisting of a zinc and copper 
plate, connect- 
ed together by 
means of a wire 
bent so as to 
form a flat coil, 
is floated by 

means of a cork in acidulated 
water. The current runs round 
the coil in the direction of the 
arrows, and the arrangement, 
obeying the magnetic influence 
of the earth, turns, with its plane 
pointing north and south, just as 
a magnet would do if introduced into the interior of the 
coil, in the position shown in the figure by the dark line. 

Ampere infers, from the analogy of these instruments, 
that the magnet owes its qualities to electric currents cir- 
culating in it in a transverse direction. The directive 
action of the magnetic needle or the electric helix depends 
on the reaction of electric currents circulating in the 
earth, due to the unequal heating of its surface by the 
rays of the sun. 

We have seen that an electric current can develop 
magnetism in a bar of iron or steel; in the former, tran- 
Fig. 129. b sient, in the latter, perma- 

nent magnetism. Thus, if 
the iron bar, 2s, Fig. 129, 
saemn be placed in the axis of a 
y helix of copper wire, along 
a F which a current is flowing, 
the current develops magnetism in the bar. It was dis- 
covered by Faraday that the converse also holds good, 
and that a magnet can give rise to an electric current. 
Thus, in Pig. 129, let the terminations a@ 6 of the helix c 


Describe the phenomena of the electro-dynamic helix, Fig. 127. De- 
scribe those e flat coil. What is Ampere’s theory of the nature of 
the magnet? magnetized bar be made to develop electric currents ? 


MAGNETO-ELECTRIC CURRENTS. 139 


be brought in contact, and having placed a soft iron bar, 
m s, within it, let the bar be made magnetic by the ap- 
proach of a strong magnet. Ass assumes the magnetic 
condition, it generates a current, which runs through the 
helix c; and if at this moment the wires a d are drawn 
apart, a bright spark, sometimes called the magnetic 
spark, passes. It does not come, however, from the mag- 
net itself, but is due to the electric current established in 
the helix by the disturbing action of the magnet. If be- 
tween the terminations a J a slender wire is placed, it 
may be made red hot, or water may be decomposed, or 
any of the phenomena of a Voltaic battery may be exhib- 
ited by the aid of this magneto-electric current. On this 
principle are constructed the magneto-electric machines, 
of which different forms have of late been so generally 
introduced for the purpose of the medicinal application of 
electricity. They all depend essentially on the principle, 
that if we coil round a piece of soft iron a conducting 
wire, as often as the iron is magnetized, a wave of elec- 
tricity flows through the wire. 

If two conducting wires be placed parallel and near to 
each other, when an electric current is passed through 
one of them a wave-of electricity flows in the opposite di- 
rection through the other; and on the first current stop- 
ping, another wave, coinciding with it, passes through the 
second wire. ‘These momentary currents are all called, 
from the name of their discoverer, Faradian currents. 

If we take a bar of antimony, a, Fg. 130, and one of 
bismuth, 6, and having soldered themend to Fig. 130. 
end at c, pass a feeble current through them | 
in a direction from the antimony to the bis- 
muth, the temperature of the compound bar 
rises ; but if the current passes in the oppo- 
site direction, cold is produced. | By fixing 
thermometers into the substance of the bars, 
these facts may be readily verified, and in the | 
latter case, when water is placed ina depres- "> 
sion made for it in the bar, and the reduction of tempera- 
ture slightly aided, it can be frozen by the electric current. 

The same compound bar of bismuth and antimony, 


What are the properties of these currents? What is the principle of 
the magneto-electric machine? What is meant by Faradian currents ? 
What is their direction? How may heat and cold be produced by a cur- 
rent in a compound bar? 


ree 


te 


y 


140 THERMO-ELECTRIC CURRENTS. 


having its extremities connected together by a wire, when- 
ever heat is applied to the junction, an electric current sets 
from the bismuth to the antimony, and when cold is appli- 
ed, from the antimony to the bismuth. These important 
facts were discovered by Seebeck in 1822, and the cur- 
rents have been designated by him thermo-electric currents. 

For the production of these thermo-electric effects, two 
metals are not necessarily required. One end of a thick 
metallic wire being made red hot and brought in contact 
with the other, a current instantly passes from the hot to 
the colder portion, and continues to flow in diminishing 
quantities until the two ends have reached the same tem- 
perature. Or if a metallic ring be made red hot in any 
limited portion of its circumference, so long as the heat 
passes with freedom to the right hand and to the left, 
electric development does not appear; but if we touch 
with a cold rod the hot portion, abstracting thereby a por- 
tion of its heat, a current in an instant runs round it. 

It is not alone in metals that these thermo-electric cur- 
rents can be induced; other solids, and even liquids, may 
originate them. Among metals associated together, the 
relation often exhibits singular changes. Copper and iron 
form a very active couple until their temperature ap- 
proaches 800° I’.; the current then stops, and on contin- 
uing the heat, another current is developed, passing in the 
opposite way. ‘The same takes place with a pair of sil- 
ver and zinc, at a temperature of 248° F’. 

Thermo-electric currents generated in metallic bars, 
experiencing little resistance to conduction, have therefore 
very little tension ; the thinnest stratum of water is a per- 
fect non-conductor to them. 

In any thermo-electric couple the quantity of electrici- 
ty evolved depends upon the temperature ; but, as I have 
shown in a memoir on the electro-motive power of heat, 
inserted in the Philosophical Magazine for June, 1840, it 
is not directly proportional to it, except through limited 
ranges of temperature; we can not, therefore, make use 
of these currents for the determination of temperatures 
with accuracy, on the hypothesis of the proportionality of 
the quantities of electricity to the quantities of heat. 


What are thermo-electric currents? Can they be generated by one 
metal only? Can they originate in other solids besides metals, and in 
liquids? What is the action of a pair of copper and iron, and silver and 
zinc? Why have they so little tension? Is the quantity of electricity 
evolved proportional to the temperature ? 


ws 


THE THERMO-ELECTRIC MULTIPLIER. 141 


By joining a system of bars alternately together, we 
may reduplicate the effects of a single pair. As might 


have been predicted on the theory of Ohm, and as I have 


shown in the memoir just quoted experimentally, where 
the conducting resistance remains the same, the quantity 
that passes the circuit is directly proportional to the num- 
ber of pairs. It is upon this principle that, several years 
ago, M. Melloni constructed his thermo-electric multiplier, 
fig.131. Thirty or forty pairs of minute bars of bismuth 
Fig. 131. 
Cn fc 


and antimony IF F, with their alternate ends soldered to- 
gether, are arranged in a small space, so that their ends 
expose an area not exceeding the section of the bulb of a 
common thermometer, the current that passes from this 
pile being so conducted, by means of wires C C, as to de- 
flect a magnetic needle. To the thermo-electric pile a gal- 
vanometer is therefore attached, as seen in Fug. 132, 


a 


iit 
IH 
i 


What is the principle ofthe thermo-electric multiplier of Melloni? How 
is it constructed ? 


142 THERMO-ELECTRIC PAIRS. 


which represents the whole instrument in section and 
perspective. A B C is the coil of the multiplier, its ter- 
minal wires ending in the connecting cups, F F’. The 
coil rests on a plate, D E, which can be made to revolve 
by means of a wheel and screw connected with the but- 
ton G. An astatic combination of needles is support- 
ed by the frame Q M N, by a single silk thread, V L. 
To protect the instrument from currents of air, it is coy- 
ered with a glass cylinder, R L, strengthened by brass 
rings, PS, Y Z;. K T is the basis.on which the cylinder 
rests. The angle of deflection of the needle is taken as 
the measure of the temperature. Of all thermometers, 
this is by far the most sensitive. 
I have introduced certain improvements in the con- 
Fig. 133. struction of the thermo- 
electric element. Let 
a, Fig. 133, be a bar of 
antimony, and 6 a bar 
of bismuth. Let them 
be soldered along c d, 
and at d let the temper- 
ature be raised; a cur- 
q!! Bl! rent is immediately ex- 
cited, but this does not 
pass round the bars a 3, 
inasmuch as it finds a shorter and readier channel through 
the metals between ¢ and d, as indicated by the arrows. 
Nor will the whole current pass round the bars until the 
temperature of the soldered surface has become uniform. 
An improvement on this construction is, therefore, such as 
is represented at a! b’, which consists of the former ar- 
rangement cut out along the dotted lines; here the whole 
current, as soon as it exists, is forced to pass along the 
bars. One of the best forms of a thermo-electric pair is 
given at a’ b!’, where a” is a semi-cylindrical bar of an- 
timony and 6” of bismuth, united by the opposite corners 
of a lozenge-shaped piece of copper,c. The heat is to fall 
on ¢, which becomes hot and cold with promptitude, and 
determines a current. 
Besides the various sources of electricity to which I 
have referred, there are certain animals which possess 


In what manner may the simple thermo-electric pair be improved ? 
What is animal electricity ? 


ANIMAL ELECTRICITY. 143 


the power of controlling the equilibrium of the electric 
fluid in their neighborhood at will, being accommodated 
for this purpose with a specific nervous apparatus. The 
torpedo, a fish living in the Mediterranean, and the gym- 
notus electricus, which is found in some of the fresh-wa- 
ter streams of South America, have this property. The 
shock of the torpedo passes through conducting bodies, 
but not through non-conductors. A gymnotus which was 
exhibited in London was found to deflect a magnetic nee- 
dle powerfully by its discharge. A steel wire was mag- 
netized by it, and iodide of potassium decomposed. In an 
interrupted metallic circuit a spark was seen, and the in- 
duced spark was also obtained by a coil. The current 

assed from the anterior to the posterior parts of the animal. 
Mr. Faraday, the author of these experiments, calculates 
that the quantity of electricity passing at each discharge 
of the fish was equal to that of a Leyden battery contain- 
ing 3500 square inches charged to its highest degree, and 
this could be repeated two or three times with scarce a 
sensible interval of time. 

As the electricity which these animals discharge de- 
pends on their nervous action, the production of it is at- 
tended with a corresponding nervous exhaustion. It is, 
therefore, not improbable that the converse of these actions 
holds good, and hereafter it will be found that electricity 
reacts on the nervous fluid. 

In concluding this subject, I may mention a source of 
electricity which of late has excited much attention. When 
high-pressure steam is allowed to escape from a boiler 
through a narrow jet, a powerful excitement is produced, 
and sparks many feet in length may be obtained. The 
effect appears to be due to the friction of minute. drops of 
water against the tube through which the steam is es- 
caping. 


By what animals is it exhibited? What effects have been produced 
by the electricity of the gymnotus? What is the computed quantity of 
the electricity in each discharge? Why is this electric development at- 
tended with a nervous exhaustion? What is the cause of electricity pro- 
duced by steam? 


PART IIL 


LECTURE XXXIII. 


Tur Nomencuature.— The French Nomenclature. — 
Table of Elementary Bodies.—Nomenclature for Com- 
pound Bodies, Acids, Bases, and Salts. 


Unrtit after the discovery of oxygen gas, the nomencla- 
ture of chemistry was very loose and complicated. The 
trivial names which were bestowed on various bodies had 
frequently little connection with their properties ; some- 
times they were derived from the name of the discoverer, 
or sometimes from the place of his residence. Glauber 
salt takes its designation from the chemist who first 
brought it into notice, and Epsom salt from a village in 
England, in which it was at one time made. 

It is obvious that such a system of nomenclature, as 
soon as the number of compound bodies increased, would 
not only become unmanageable, but, by reason of the im- 
possibility of carrying in the memory such a mass of uncon- 
nected terms, offer a very serious impediment to the prog- 
ress of the science. Lavoisier and his associates, about the 
close of the last century, constructed a new nomenclature, 
with a view of avoiding these difficulties. Its principles, 
with some modifications, are now universally received. 
The following is a brief exposition of it: 

Natural bodies may be divided into two classes, simple 
and compound; the former are also calledelementary. By 
simple or elementary bodies we mean those which have 
not as yet been decomposed. 

Among simple substances, those which have been known 
for a long time retain the names by which they are pop- 
ularly distinguished; thus, gold, iron, copper, &c.; and 
when new bodies belonging to this class are discovered, 


What was the nature of the nomenclature used by the older chemists ? 
When was the system now in use invented? What is meant by simple 
or elementary bodies? Whatis the rule for the old simple bodies ? What 
for those newly discovered ? 


= 


Padi 


NOMENCLATURE FOR SIMPLE BODIES. 145 


they are to receive a name descriptive of one of their 
leading properties; thus, chlorine takes its name from its 
greenish color, and iodine from its purple vapor. It is to 
be regretted that this rule has often been overlooked. 

Some doubt exists as to the exact number of the ele- 
mentary bodies. It may be estimated at 58, including 
three metals recently discovered, the titles of which have . 
not yet been completely established. 

Of the list of elementary bodies, the metals form by far 
the larger portion, there being 45 of them; the remaining 
13 are commonly spoken of as non-metallic substances. 
By some authors these are called metalloids, in contra- 
distinction to the metals, an epithet which, however, is 
very objectionable. 


Table of elementary or simple Substances, with their Symbols and Atomic 
Weights. 


Non-metallic Elements. |Symbols.| At. wts. Metallic Elements. Symbols.| At. wts. 


Oxygen. O. 8°013] Erbium ,.. . «.}.Ei ——4 
Hydrogen . BSE L000 Fe TOP sie, sole to Us — 
Nitrogen N. 14:19 | Manganese . ./| Mn. 27°72 
Sulphur . s. Toa Tron er 42n-.. Pare Be! 27°18 
Phosphorus R- 35.72) 1. Cobalt nai an eto giOe 29°57 
Carbon . C. GO4aioNickele oo ooose ONT. 29°62 
Chlorine . Cl. SOAP EZANG eee ete Ze 32°31 
Bromine . 5 SBE: 78°39 | Cadmium® .. + 1.{+@d. 55°83 
loding: 3) 2 #4... |. 1: 126:oie | lseade. ou). tee ee Ds 103°73 
Fluorine He 18°74 Hi bah ad. blll alg cenit adhe 66 58°92 
Boron . ys B. 10-91] ‘Biamuth’. 7: 3 Br 71:07 
Silene ok metas A fake 22°22 | Copper... ., 24, Cu, 31-71 
Selenium .... | Se. 39655 | MUranivnremee = a) ele Ue 217°20 
Mercury. . . .| Hg. | 202°87 

Metallic Elements. Silver. . . - | Ag. | 108°31 
Potassium «. : .. | K. 39°26 | Palladium ~ lees 53°36 
oun et NA 23°31 | Rhodium A il 3 52°20 
Tsttnmirtig: Fees Ue Lae 6°44 | Iridium . Nee Nb y 98°84 
Bariam, oie, - f8. 94) /68°66, | Platinom,.« .,.0| Pt 98°84 
Strontium . . .{| Sr. 43°85 | Gold . See ees 199°2 
Calcraniniee & eeu Cas 20:52 |) Osintum'. 04), i Ost 99°72 
Magnesium . .| Mg. 12:89] Titanium . . «| Ti. 24:33 
Aluminum’... |) AL 13273 71> Tantalumess i .5 aca: 184:90 
Glucinum .. .|G. 20°04 1° Telluriam'*.; = =? Te. 64:25 
Metripee Tyce) py: 32°25 | Tungsten . . .| W. 99°70 
Arcanum... |Z: 33°67 | Molybdenum . . | Mo. 47:96 
Suter 4 Gy a re D830 le Vanadiumiers seat sve 68°66 
Gorigers: Sta Te Ca, 46.05 | Chromium . . .|]| Cr. 28°19 
Lanthanum . .| La. —— | Antimony » > i+. /.- ; Sbi 64°62 
Didymium . . .| D. — | Arsenic. . . .| As. 37°67 


Compound bodies may, for the most part, be divided 


What is the number of the elementary bodies? Of these, to what class 
do the greater part belong?) What are the symbols for the elementary 
bodies? What are their atomic weights ? , 


146 NOMENCLATURE FOR COMPOUNDS. 


into three groups: acids, bases, and salts. By an acid 
we mean a body having a sour taste, reddening vegetable 
blue colors, and neutralizing alkalies; by a base, a body 
which restores to blue the color reddened by an acid, and 
possessing the quality of neutralizing the properties of an 
acid ; by a salt, the body arising from the union of an acid 
and a base. These definitions, however, are to be receiv- 
ed with considerable limitation. 

The nomenclature for acid substances is best seen from 
anexample. Thus, sulphur and oxygen unite to form an 
acid: itis called sulphuric acid; the termination in zc being 
expressive of that fact. But very frequently two substances 
will form more than one acid, by uniting in different pro- 
portions; in this case the termination in ows is used; thus 
we have sulphurous acid; so called because it contains less 
oxygen than sulphuric. ‘The prefix “ hypo” is also used, 
as in hyposulphurous and hyposulphuric acids: it indicates 
acids containing /ess oxygen than sulphurous and sulphuric 
acids. ‘The prefix “ hyper’’ is used in the same way; thus, 
hyperchloric acid, an acid containing more oxygen than | 
chloric acid. 

With respect to bases, the generic termination is in zde. 
If oxygen and lead unite, we have oxide of lead, and in 

- the same manner we have chlorides, bromides, iodides, 
and fluorides. And if these elements form compounds in 
more proportions than one, we indicate their proportion 
by the Greek numerals protos, deuteros, tritos; thus we 
have protoxides, deutoxides, tritoxides ; the protoxide of 
lead contains one atom of oxygen and one of lead, the 
deutochloride of mercury two atoms of chlorine and one 
of mercury, &c. In the same manner, the prefixes sub, 
sesqui, and per are used; thus, a suboxide contains the 
lowest proportion of oxygen, a peroxide the highest pro- 
portion, and a sesquioxide intervenes between a protoxide 
and a deutoxide, its oxygen being in the proportion of one 
atom and a half. 

By an alloy, we mean the substance arising from the 
union of two metals; thus, copper and zinc unite to form 


Into what groups may compound bodies be divided? What is the defi- 
nition of an acid? What is a base? Whatisasalt? What do the ter- 
minations zc and ows indicate? What is the meaning of the prefixes hypo 
and hyper? What does the termination zde signify 1 What the prefixes 
protos, deuteros, and tritos, sub, sesqui, and per? What is an alloy and 
an amalgam ? Wai 


’ 


+. 


METHOD OF SYMBOLS. 147 


brass, which is an alloy. If one of the metals is mercury, 
the compound is called an amalgam. And when sulphur, 
phosphorus, carbon, and selenium unite with metals, or 
with each other, the termination wret is used; thus we 
have sulphurets, phosphurets, carburets, &c. 

With respect to the nomenclature for salts, the termi- 
nations ate and ite are used to indicate acids in tc and ous 
respectively. The sulphate of potash contains sulphuric 
acid, and the sulphite of potash sulphurous acid. And 
as we have already seen that different oxides arise by the 
union of oxygen in different proportions, and these bodies 
frequently give rise to different series of salts, the opera- 
tion of the nomenclature may be readily traced; thus, 
the protosulphate of iron is the sulphate of the protoxide 
of iron, but the persulphate of iron is a sulphate of the 
peroxide, and the deutosulphate of platinum a sulphate 
of the deutoxide of platinum. When the relative quan- 
tity of the acid and base varies, Latin numerals are em- 
ployed; thus the bisulphate of potash contains two atoms 
of sulphuric acid and one of potash. 

Salts are said to be neutral if neither their acid nor 
base be in excess. If the acid predominates, it is an acid, 
or super-salt ; if the base, it is a basic, or sub-salt. 


LECTURE XXXIV. 


Tue Sympois.—Fazlure of the Nomenclature in the Case 
of Complex Compounds. — Failure in Difference of 
Grouping.— Symbols for elementary Bodives.— Expres- 
sions for several Atoms.— Use of the Plus Sign—Ex- 
pressions for Grouping. 

So long as the constitution of compound bodies is sim- 
ple there is no difficulty in applying the nomenclature, or 
in recognizing from the name of the compound the nature 
and proportions of its constituents. Thus, protoxide of 
hydrogen clearly indicates a body in which one atom of 
oxygen is united with one of hydrogen, bisulphate of pot- 
ash a body composed of two atoms of sulphuric acid and 


When is the termination uwret employed? What do the terminations 
ate and zfe indicate? What is the nomenclature for the salts? What is 
aneutral salt? What is an acid, or super-salt? What is a basic, or sub- 
salt? Under what circumstances does the nomenclature apply, and when 

does it fail? 


148 IMPERFECTIONS OF THE NOMENCLATURE. 


one of potash, and even in more complicated cases, such 
as the sulphato-tricarbonate of lead, &c., the same prin- 
ciples will serve as a guide. 

But when compound bodies consist of a great number 
of atoms, the nomenclature ceases to be of any service. 
Thus, starch is composed of twelve atoms of carbon, ten 
of hydrogen, and ten of oxygen. Jibrin is composed of 
forty-eight atoms of carbon, thirty-six of hydrogen, four- 
teen of oxygen, six of nitrogen, with minute but essential 
quantities of sulphur and phosphorus. On the principles 
of the nomenclature, it would be difficult to give to the 
first a technical name, and in the case of the latter im- 
possible. 

The peculiarity of organic compounds is, that they 
contain but few of the elementary bodies, being chiefly 
made up of carbon, hydrogen, oxygen, and nitrogen ; but 
these, as in the case of fibrin, unite in a very complicated 
way, very often hundreds of atoms being involved. The 
nomenclature is therefore inapplicable to organic chemistry. 

There is also another very serious difficulty in its way. 
It has been discovered that compounds may consist of the 
same elements, united in precisely the same proportions, 
so that when they are analyzed they yield precisely the 
same results, and yet they may, in reality, be very differ- 
ent substances. Identity in composition is no proof of 
the sameness of bodies. ‘Thus we may have the same 
elements uniting together in the same proportion, and 
yielding a solid, a liquid, or a gas indifferently. This re- 
sult may depend on several causes, as will be presently 
explained; but among these causes I may here specify what 
is termed by chemists ‘ Grouping.” ‘Thus, suppose four 
elementary bodies, A BC D, unite together, there is ob- 
viously a series of compounds which may arise by per- 
muting or grouping them differently, as in the following 
example : : 


(1) leben ieae 

(2) A + BD. 

(3) a0 + CB. 
&c. &c. 


What is the peculiarity of organic compounds? Why is the nomencla- 
ture inapplicable to organic chemistry? Is identity of composition any 
proof of the identity of bodies ? What is meant by grouping? Give an 
example. 


METHOD OF SYMBOLS. 149 


The method of symbols which is designed to meet these 
difficulties, and is, in reality, an appendix and improve- 
ment upon the nomenciature, was originally introduced 
by Berzelius; but the form which is now most commonly 
adopted is that of Liebig and Poggendorff. The adyan- 
tages which have been found to accrue from it are so 
great, that it is now introduced into every part of chemis- 
try, so that it is impossible to read a modern work on this 
science without having previously mastered the symbols. 

The student should not be discouraged at the mathe- 
matical appearance of chemical formule. He will find, 
by a little attention, that they are founded upon the sim- 
plest principles, and involve merely the arithmetical 
operations of additionand multiplication. The following 
is a brief exposition of their nature : 

For the symbol of an elementary substance we take the 
first letter of its Latin name, as is shown in the table 
given in the last lecture. Those symbols should be com- 
mitted to memory. But as it happens that several sub- 
stances sometimes have the same initial letter, to distin- 
guish between them we add a second small letter. Thus, 
carbon has for its symbol C.; chlorine, Cl. ; copper (cu- 
prum), Cu.; cadmium, Cd., &c. It may be observed that 
in the case of recent Latin names the German synonym 
is always used; thus, potassium is called kalium in Ger- 
many, and has for its symbol K.,; sodium is called natri- 
um, and has for its symbol Na., &c. 

But a symbolic letter standing alone not merely repre- 
sents a substance; it farther represents one atom of it; 
thus, C means one atom of carbon, and O one atom of 
oxygen. 

If we wish to indicate that more than one atom is pres- 
ent, we affix an appropriate figure, as in the following 
examples: C,,.H,).O,.. Thus, nitric acid is composed 
of one atom of nitrogen united to five of oxygen, and we 
wiite it NO,. 

When a compound, formed of several compounds, is to 
be represented, we make use of an intervening comma; 
thus, strong oil of vitriol is composed of one atom of sulphur 


What are the symbols for elementary bodies? When two bodies be- 
gin with the same letter, how are the symbols arranged? What does a 
single symbol standing alone represent? How are more atoms than one 
represented? How is the comma employed? 


s 


Se eee Le ee ee ee a 


150 METHOD OF SYMBOLS. 


and three of oxygen, united with one atom of water, which 
is composed of one atom of oxygen and one of hydrogen, 
and we write it SO,, HO. 
If we desire to indicate that compounds are united with 
a feeble affinity, we make use of the sign +; thus, the 
composition of sulphuric acid may be written SO,, or 
SO,+ O, the latter formula implying that one of the atoms 
of oxygen is held by a feebler affinity than the other two. 
When a large figure, or coefficient, is placed on the 
same line as the symbol, and to the left of it, it multiplies 
that symbol as far as the first comma or + sign; or, if the 
formula be placed in a parenthesis, it multiplies every 
letter under the parenthesis; thus, 2SO,, KO, HO or 
2S0,+KO+HO mean two atoms of sulphuric acid 
united with one of potash and one of water, forming the 
bisulphate of potash; but 2(SO,;, KO, HO.) would repre- 
sent two atoms of a salt composed of one of sulphuric acid, 
one of potash, and one of water, the figure here multiply- 
ing all under the parenthesis. 
The advantages which arise from the use of these sim- 
le rules are very great; we can, even with the most 
complex bodies, not only express their composition, but 
also the molecular arrangement, or grouping of their 
atoms; we can follow them through the most intricate 
changes, and without difficulty trace out their metamorph- 
oses. For example, analysis shows that alcohol is com- 


posed of 

C., H,, O2, 
but many facts in its history lead us to know that its mole-- 
cular constitution is 

(C,H;)O+HO ; 

that is to say, it contains a compound radical C,H,, to 
which the name of ethyl has been given, and this fact 
being understood, we see at once that upon the principles 
of the nomenclature the true name for alcohol is the hy- 
drated oxide of ethyl; moreover, alcohol is derived by 
processes of fermentation from sugar. The constitution 
of dry grape sugar is 

Cros ET», Or. 


What is the use of the sign plus? How far does a coefficient multi- 
ply? What are the advantages arising from the symbols? Give an ex 
ample in the case of alcohol. 


LAWS OF COMBINATION. 151 


This complex atom, under the influence of active yeast, is 
split into 

2 Qypdd, Oz) #2 tt, 460.03), 
that is to say, into two atoms of alcohol and four of car. 
bonic acid gas; and, accordingly, we find, during fermen- 
tation, that the sugar disappears, alcohol forming in the 
liquid, and carbonic acid gas escapes. 

The student should accustom himself to the translation 
of the nomenclature into symbols, and symbols into the 
nomenclature, in cases where it is possible, for it is abso- 
lutely essential that he should be perfectly familiar with 
the process. 


LECTURE XXXV. 


Tue Laws or Compination.—Lavw of Fixed Proportions. 
—Numerical Law.— Multiple Law.— Modes of express- 
ing Composition.—Proportions, Equivalents, and Atomic 
Weights—Relation between Combining Volumes and 
Atomic Weights.— Table of Specific Gravities and 
Atomic Weights. 


Ir has been shown, in the first and second lectures, 
that material substances possess an atomic constitution, 
and all the phenomena of chemistry bear out this conclu- 
sion. It follows, therefore, when substances combine 
with each other and give rise to new products, the union 
takes place by the atoms of the one associating themselves 
with the atoms of the other, and as these atoms possess 
weight and other properties which are specific, there are 
certain circumstances, easily foreseen, which must attend 
such combinations. 

1st. The constitution of a compound body must always 
be fixed and invariable. ‘This arises from the fact of the 
unchangeability of the properties of atoms; one atom of 
water will always be composed of one atom of oxygen 
and one of hydrogen; one atom of carbonate of lime will 
always consist of one atom of carbonic acid and one of 
lime. Or, more generally, if a good analysis of water has 
shown that nine grains of that substance contain eight 


In what manner does the combination of bodies take place ? What is 
meant by the law of fixed: proportions ? 


152 = NUMERICAL AND MULTIPLE LAWS. 
v4 


grains of oxygen and one of hydrogen, every subsequent 
analysis will correspond therewith. 

2d. The proportions in which bodies are disposed to 
unite with each other can always be represented by cer- 
tain numbers ; these numbers being, in fact, the relative 
weights of their atoms. Thus water is composed of an 
atom of oxygen and one of hydrogen, and inasmuch as 
the oxygen atom is eight times heavier than that of hy- 
drogen, it necessarily follows that in every nine parts of 
water we shall have eight of oxygen and one of hydro- 
gen. These numbers are, therefore, spoken of as the 
combining proportion or equivalents of the substances 
to which they are attached. If, farther, we examine, 
when oxygen and sulphur unite, what are the relative 
quantities, we shall find that eight parts of oxygen com- 
bine with sixteen of sulphur, “forming hyposulphurous 
acid. And ifsulphur and hydrogen unite, it will be found 
that sixteen of sulphur combine with one of hydrogen. 
In this manner, by examining the various elementary 
bodies, we find that certain numbers are expressive of the 
proportions in which they are disposed to unite, and these 
numbers represent the relative weight of their atoms; 
thus, if 1 be taken as the atomic weight of hydrogen, that of 
oxygen is 8, that of sulphur 16, &c.; the atomic weights of 
the elementary bodies have been given in Lect. XX XIII. 

3d. If two substances unite with each other in more 
proportions than one, those proportions bear a very simple 
arithmetical relation to one another; thus, 14 grains of 
nitrogen will successively unite with 8, 16, 24, 32, 40 
grains of oxygen, forming successively the protoxide of 
nitrogen, the deutoxide, hyponitrous acid, nitrous acid, 
and nitric acid. And when the numbers expressing the 
amount of oxygen are examined, it is seen that they are 
in the second twice, in the third thrice, in the fourth four 
times, and in the fifth five times the amount of the first; 
they are, therefore, simple multiples of it. The reason of 
this is plain when we write the constitution of these bodies 
in symbols; they are successively, 


NO? ANOS YANO, SINOT NO, 5 


What by the numerical law? Give an example in each case. What 
do the numbers represent? Give examples of these numbers. What is 
meant by the multiple law? Give an example of it in the case of the com- 
pounds of nitrogen and oxygen. 


ATOMIC WEIGHTS OR EQUIVALENTS. 153 


and if one atom of oxygen weighs 8, two must weigh 16, 
three 24, four 32, &c.; the multiple law, therefore, is a 
necessary consequence of the combination of atoms. 

Observation has shown that there are two series ac- 
cording to which bodies may unite with each other. 

(1.) 1 atom of A may unite with 1, 2, 3, 4, 5, &c., atoms of B. 

(2.) 1 atom of A may unite with 4, 1, 1}, 2, 2}, 3, &c., atoms of B. 

But as an atom is indivisible, there can be no such 
thing as a half atom; consequently the second series be- 
comes, 


(3.) 2 atoms of A may unite with 1, 2, 3, 4, 5, &c., atoms of B. 


The three foregoing laws are known under the name 
of the laws of combination; they are the law of definite 
proportions, the law of numbers, and the multiple law. 

There are three ways in which the composition of a 
substance may frequently be expressed: 1, by atom; 2, 
by weight; 3, by volume. Thus, the constitution of wa- 
ter, by atom, is one of oxygen to one of hydrogen; by 
weight, it is one of hydrogen to eight of oxygen; and by 
volume, two of hydrogen to one of oxygen. ‘These dif- 
ferent modes of expression involve nothing contradictory ; 
they are all reconciled by the statement that the atom of 
oxygen is eight times as heavy as that of hydrogen, but 
only half the size. 

By some authors the terms combining proportion and 
equivalent are used; they have the same signification as 
atomic weight. And as we know nothing of the absolute 
weight of atoms, but only their relative proportions to 
each other, we may select any substance with which to 
compare all the rest, and make it our unit or term of com- 
parison. In this book hydrogen is employed for this pur- 
pose, and its atomic weight is marked 1; on the Continent 
of Europe oxygen is selected, and marked 100. It is 
obvious that this does not affect the relationship of the 
numbers, for it is the same thing whether we state the 
atomic weights of hydrogen and oxygen as.1 to 8, or as 
121 to 100. 


What are the two series in which bodies may unite? In what ways 
may the composition of a body be frequently expressed? How is the ap- 
parent contradiction of these statements reconciled? "What do proportion 
and equivalent signify? What is the substance with which all others 
are compared for their atomic weights in this book? What other stand- 
ards might be employed ? 


154 SPECIFIC GRAVITIES AND ATOMIC WEIGHTS. 


Combinations may take place in two different ways: 
Ist, in definite proportions; 2d, in indefinite proportions. 
It is to the former that all the foregoing observations and. 
laws apply. One grain of hydrogen will not unite with 
nine or seven grains of oxygen, but only with eight. But 
one drop of spirits of wine may combine with one of wa- 
ter, or with a pint, or a quart, or ten gallons. This is 
what is understood by union in indefinite proportions. 

When two gaseous bodies unite, their combining pro- 
portions bear a simple relation to mPa other ; one volume 
of hydrogen unites with one of chlorine, and produces 
two volumes of hydrochloric acid. And in the case of the 
five compounds of nitrogen just referred to, two volumes 
of that gas combine successively with 1, 2, 3, 4, 5 of 
oxygen. 

A. relation, therefore, exists between the combining 
volume and the atomic weight of gaseous bodies. If the 
weight of a given volume of oxygen be called 1000, that 
of an equal volume of hydrogen will be 625, these num- 
bers representing, of course, the specific gravity of the 
two gases. The proportion in which they unite is one 
volume of oxygen to two of hydrogen to form water; the 
relative weights of these quantities, therefore, would be 
100:0 to 6°25 x 2, that is, 100°0 to 12°50, but these num- 
bers are the atomic weights of the bodies respectively. 
From such considerations, it was at one time supposed 
that, in the case of all gases, the specific gravities would 
correspond to the Mone weights, Experience has, how- 
ever, shown that this is not the case, as is seen in the 
following table : 


Specific Gravities. Chemical Equivalents. 
i = 7 F ig 19 


Gas, or Vapor. 


Carbon (aypothetical) . 
Chlorine 


‘What are the two modes of combination? What relation is observed 
when gases combine by volume? What is the relation between specific 
gravities and atomic weights ? 


CALCULATION OF SPECIFIC GRAVITIES. 155 


From this it is seen, that if the combining volume of 
hydrogen, nitrogen, or chlorine be taken as unity, that of 
oxygen is one half, of vapor of phosphorus one fourth, and 
of vapor of sulphur one sixth. 


LECTURE XXXVI. 


Constitution or Bopres.—Calculation of Specific Grav- 
éties — Crystallization —Systems of Crystals.—Dimor- 
phism.—Isomorphism.—Isomorphous Groups.—Isomer- 
esm.— Metameric and Polymeric Bodies. — Allotropic 
States of Bodies. 

On the principles which have just been developed, we 
can often calculate the specific gravity of a compound gas 
with more accuracy than it can be determined experi- 
mentally. Thus, hydrochloric acid, which consists of 
equal volumes of chlorine and hydrogen united, without 
condensation, must have a specific gravity of 1:2695, be- 
cause the specific gravity of hydrogen being 0:0690, and 
that of chlorine 2°4700, the sum of which, 2°5390, is the 
weight of two volumes of hydrochloric acid, and, there- 
fore, if we divide by 2, the quotient, 1:2695, is equal to 
the weight of one volume; or, in other words, the specific 
gravity of the compound gas. 

Sometimes, also, we can determine the specific gravity 
of a vapor by calculation when it is impessible to do so 
experimentally. Assuming that one volume of carbonic 
acid gas contains one volume of oxygen and one of car- 
bon vapor, we have, 


Specific gravity of carbonic acid. . . 175238 
He ke oxygen. . «,a «191025 
4 be carbon vapor. . . ‘4213 


The hypothetical specific gravity of the vapor of carbon 
is therefore °4213. 

The rule for the calculation of specific gravities, on the 
foregoing principles, is, “ Multiply the specific gravities 
of the simple gases or vapors respectively by the volumes 
in which they combine, add those products together, and 


How may the specific gravity of a compound gas be determined? How 
is the hypothetical specific gravity of the vapor of carbon determined ? 
What is the rale for the calculation of the specific gravities of compound 
gases from those of their constituents ? 


156 SYSTEMS OF CRYSTALLIZATION. 


divide the sum by the number of volumes of the compound 
gas produced.” 

It frequently happens that substances assuming the 
solid form, from the liquid or vaporous states, take on a 
geometrical figure, being terminated by sharp edges and 
solid angles; under such circumstances, they are said to 
crystallize. Thus, common salt will crystallize i in cubes, 
and nitrate of potash in six-sided prisms. 

The various geometrical forms which crystals can thus 
assume may be divided into six classes, or systems : 


(1.) The Regular system. 

(2.) The Rhombohedral system. 

(3.) The Square Prismatic system. 

(4.) The Right Prismatic system. 

(5.) The Oblique Prismatic system. 

(6.) The Doubly Oblique Prismatic system. 


This division is founded on the relations of certain lines, 
or axes, which may be supposed to be drawn through the 
center of the crystal round which its parts are symmetri- 
cally arranged. 


THE REGULAR SYSTEM. 


This has three equal axes at right angles to each other. 
Fig. 134. 


The letters @ a show the direction of the axes. The 
figure (Ig. 134) represents, 1. The cube; 2. Regular oc- 
tahedron ; and, 3. Rhombic dodecahedron. 


THE SQUARE PRISMATIC SYSTEM. 


This has three axes, two of which are equal, and the 
third of a different length. 

a a is the principal axis; 4 6 the secondary one. In 
the figure (ig. 135), 1 is a reght square prism, with the 
axes on the center of the sides, 66; 2 is a right square 


What are the six systems of crystallization? Upon what fact is this 
division founded? In the regular system, what is the relation of the axes * 
In the square prismatic system, what is their relation ? 


SYSTEMS OF CRYSTALLIZATION. 157 


Fig. 135. 


prism, with the axes in the edges; 3 and 4 corresponding 
right square octahedrons. 


THE RIGHT PRISMATIC SYSTEM 
has three axes, a a, b 6, c c, of unequal lengths, at right 
angles to each other. 

Fig. 136. 


a 


In the figure (Fig.136), 1 is aright rectangular prism ; 
2. Right rhombic prism ; 3. Right rectangular based octa- 
hedron; 4. Right rhombic based octahedron. 


THE OBLIQUE PRISMATIC SYSTEM 
has three axes, which may be unequal; two are placed 
Fig. 137. 


What is it in the right prismatic? In the oblique and double oblique 
prismatic systems, what is it? 


158 SYSTEMS OF CRYSTALLIZATION. 


at right angles.to each other, and the third is oblique to 
one and perpendicular to the other. 

In the figure (fg. 137), 1 is an oblique rectangular 
prism ; 2. Oblique rhombic prism ; 3. Oblique rectangular 
based octahedron ; 4. Oblique rhombic based octahedron. 


THE DOUBLY OBLIQUE PRISMATIC SYSTEM 


has three axes, which may be all unequal and all oblique. 
Fig. 138. 


In the figure (Ig. 138), 1 and 2 are doubly oblique 
prisms ; and 3 and 4 doubly oblique octahedrons. 


THE RHOMBOHEDRAL SYSTEM 


has four axes, three of which are equal in the same 
plane, and inclined at angles of 60° ; the fourth, which is 
the principal axis, is perpendicular to all. 

Fig. 139. 


In the figure (F%g. 139), 1 is the regular six-sided prism ; 
2, the dodecahedron; 3. Rhombohedron ; 4. another dode- 
cahedron. 

It often happens, owing to a change in the’ deposit of 
new matter on a crystal while forming, that other figures 
than the proper one are produced ; thus, the cube may 
pass into the octahedron, as shown in fg. 140. 


How many axes are in the rhombohedral system, and what is their re- 
lation? In what manner may crystals of one form pass into those of 
another, as the cube into the octahedron? } 


GONIOMETERS. .. ae 


LN I 
CY) RD GA 


The effect may, perhaps, be better conceived by imagin- 
ing the solid angle of the cube 1 to be cut off by planes 
equally inclined to the constituent faces. 2 represents an 
increased removal of the same kind; 3 one still farther 
advanced. 

Sometimes it happens that each alternate plane of a 
crystal grows at the expense of the adjacent one, giving 
rise to hemthedral, or half-sided crystals, as is shown in 
Fg. 141, which represents the tetrahedron, arising in this 
manner from the octahedron by the growth of each alter- 
nate face. 1. The octahedron partially modified; 2. The 
change farther advanced; 3. The tetrahedron completed. 


Fig. 141. 


PN} 7 2 
The angles of crystals are measured by goniometers, of 
which there are several Fig. 142. 
kinds; as the common goni- 
ometer, and Wollaston’s re- 
flecting goniometer. This ¢ 
instrument is represented 
in Ig. 142. The crystal 
to be measured, f, is fixed 
upon a movable support, 
d, which is in connection 
with the button - headed 
axis of the goniometer, 0, 
which passes through a lar- 
ger axis in the upright, 3. 
a is a divided circle, and 
é its vernier, which is fixed immovyably on the upright, 6. 


What are hemihedral crystals, and how are they produced? Describe 
the use of the reflecting goniometer. 


160 DIMORPHISM. 


The edge of the crystal, which is formed by the two fa- 
ces whose inclination is to be measured, is to be set par- 
allel to the axis of the instrument; and having, by means 
of the button, 0, turned the crystal until some definite ob- 
ject, such as the bar of a window, is seen distinctly reflect- 
ed from it, the larger milled head is turned, and with it 
the divided circ'e and crystal, until the same object is 
again seen by reflection from the second face. The an- 
gle through which the great circle has moved, subtracted 
from 180°, gives the angle included between the two crys- 
talline faces, or their inclination to each other. 

As a general rule, the same substance, crystallizing un- 
der the same circumstances, will produce crystals belong- 
ing to the same system. Cases, however, are known in 
which the same substance belongs to different systems. 
Thus, sulphur will crystallize in rhombic prisms, and also 
rhombic octahedrons. By dimorphous bodies we there- 
fore mean substances which will afford crystals belonging 
to two different systems. 

Dimorphism is frequently connected with the tempera- 
ture at which the crystals were produced. Thus, carbon- 
ate of lime, at ordinary temperatures, yields rhombohe- 
drons, but at the boiling point of water right rhombic 
prisms; and with this difference of form a difference of 
chemical qualities may occur; the bisulphuret of iron, 
for example, crystallizes in cubes which remain unacted 
upon by water or air; but in its right rhombic form it un- 
dergoes rapid oxydation in moist air, producing sulphate 
of iron. Commonly one of the forms of a dimorphous 
body is less stable than the other, and if the transition 
takes place abruptly, it is sometimes attended by a flash 
of light. 

It was discovered by Mitcherlich, that when different 
compound bodies assume the same form, we are often 
able to trace aremarkable analogy in their chemical com- 
position. Thus, the chloride of sodium, the iodide of: po- 
tassium, the fluoride of calcium, &c., crystallize in the 
first system. ‘These substances are all constituted upon 
a common type, in which we have one atom of a metal 


‘What is meant by dimorphous bodies? What effect has temperature on 
the formation of crystals? Is dimorphism connected with peculiarities in 
the chemical qualities of bodies? What relation is there in the form and 
composition of iodide of potassium and chloride of sodium ? 


ISOMORPHISM. 161 


united to one atom of an electro-negative radical; or, 
taking MW as the general symbol for the metals, and R for 
the electro-negative radicals, the class is constituted upon 


the type 
M, R, 


and, therefore, includes such bodies as 
KCl..NaCl..KBr.. KF ..CaF.AmC1...&c. 


Such substances are called isomorphous bodies, and the 
designations, isomorphous elements, isomorphous groups, 
are used, being derived from z60¢, equal, wopo7, form. 
Let us take a second more complicated case. The 
formula for common alum, the sulphate of alumina and 
potash, is, 
KO, SO,+ Al, O;3, 38O;+24HO. 
Ammonia alumis AmO, SO,;,-+ Al, O3, 3SO;+24HO. 
Chrome alum is KO, SO;+Cr,0;3, 3SO3+ 24HO. 
Tron alum is KO, SO;+ Fe, O3, 380; +24H0. 
And in the same way an extensive family of alums may 
be formed by the substitution of a limited number of vari- 
ous other bodies comprised in the general formula, 


mO, SO; + M, O;, 3SO; + 24HO, 


in which m represents any metal belonging to the potas- 
sium group, and JZ any one belonging to the aluminum 
group. 

All these alums crystallize with the same form, and 
such illustrations afford us reason to believe that that sim- 
ilarity of form is due, in a great measure, to the grouping 
or arrangement of the constituent atoms ; that in a com- 
pound molecule the substances which can replace one an- 
other without giving rise to a change of external form must 
have certain relationships to each other. We call them, 
therefore, esomorphous. The following ten groups have 
been established : 


1; Sesquioxide of Antimo- 
Pre re ee Ae DY 2 bs cep rct Cd, «MSOs ke 
RMON) hl. Miele dd 3. 
2: Alumina ow. 29S 5 AG Os 
Arsenious Acid (in its Sesquioxide of Iron . Fez O3 
unusual form) . . . As2 Os a Chromium Cr2z Os 


Why are they called isomorphous bodies? Give an example of iso- 
morphism in the case of the alums. What general conclusion may be 
drawn from these facts? How many isomorphous groups have been des 
termined? Enumerate the members belonging to each, 


162 ISOMERISM.—-METAMERIC AND POLYMERIC BODIES. 


Sesquioxide of Manga- 8. 
BGO ot, ke, > fd 08, O08 Oxide of Silver . . . Ag O 
4 Oxide of Sodium . . NaO 
3 2: 
Phosphoric Acid. . . P2 Os 
Arsenic Acid . . . . Asz Os matte a a Re e 
5. : Lime (in arragonite) oe Ae 
Sulphuric Acid . . . SOs Oxide of Lead . . . Pb.O 
Belenic:Acid . . ..., Se Os 10. 
NYOMIC ACIC.s Vaiwts .cee GT OR Lime (in Iceland spar) Ca O 
Manganic Acid . . . Mn Os Magnesia .. era i git o | 
6 Protoxide of Irn . . FeO 
Hypermanganic Acid . Mne O7 granny # Manganene as g 
Hyperchloric Acid . . Cl O7 fi pore ae ae ee 
Cobalt . CoO 
We gs Nickel . NiO 
Salts of Potash . . tthe) Copper . CuO 
Salts of Oxide of Am- = Lead (in 
monium... Am O plumbo calcite) . . Pb.O 


From the seaitial forms of bodies we may next turn 
to their internal constitution, calling to mind what has 
been already observed in Lecture XXXIV., that identity 
of composition by no means implies identity of character. 
Two substances may be composed of the same elements, 
united in the same proportions, and yet be totally unlike ; 
and it is obvious that this may be due to two different 
causes: Ist. Difference of grouping; 2d. Difference in 
the absolute number of atoms. 

Difference of grouping I have already explained in the 
lecture just quoted ; and with respect to difference in the 
absolute number of atoms, the effect is obvious from an 
example. Thus, we have as the constitution of 

Aldehyde : : : : ; : C,H,O2. 

Acetic ether . : * ; } ? C,H,O; 
And these bodies, if analyzed, would, of course, yield pre- 
cisely the same proportions in 100 parts, the true differ- 
ence being; that the atom of acetic ether contains twice 
as many constituent atoms as that of aldehyde, and is, 
therefore, exactly twice as heavy, though equal weights 
of the two will yield equal quantities of their constituents. 

To these peculiarities the term isomerism is applied, 
and by isomeric bodies we mean bodies composed of the 
same’ elements in the same proportion, but differing in 
properties. When isomerism arises from difference in 
gr ouping, the bodies are said to be metameric; and when 


What two causes may give to bodies of the same composition different 
characters? Give an example of the effect of difference of the absolute 
number of atoms. What is meant by isomerism? 


ALLOTROPISM. 163 


it arises from difference in the absolute number of atoms, 
they are called polymeric. 

Attention has recently been drawn to a third cause, 
which gives rise to the phenomena of isomerism: it is the 
allotropic condition of elementary bodies. Carbon, for 
example, exists under a number of different forms ; we 
find it as charcoal, plumbago, and diamond. They differ 
in specific gravity, in specific heat, and in their conduct- 
ing power as respects caloric and electricity. In their 
relations to light, the one perfectly absorbs it, the second 
reflects it like a metal, the third transmits it like glass. 
In their relation to oxygen they also differ surprisingly ; 
there are varieties of charcoal that spontaneously take 
fire in the air, but the diamond can only be burned in 
pure oxygen gas. The second and third varieties do not 
belong to the same crystalline form. 

It is now known that a great many elementary substan- 
ces are affected in this manner. I have shown that this 
is the case with chlorine gas, which changes under the in- 
fluence of the indigo rays (Phil. Mag., July, 1844). In 
the same manner, it has been long known that iron exists 
in two states: Ist. In its ordinary oxydizable state; 2d. 
In a condition in which it simulates the properties of pla- 
tinum or gold. ) 

There can be no doubt that these peculiarities are car- 
ried by these bodies when they unite to form compounds ; 
thus, for example, if carbon and hydrogen unite, it is pos- 
sible we may have three different compounds; one con- 
taining charcoal carbon, asecond plumbago carbon, a third 
diamond carbon; or, if we designate these respectively as 
Ca, CB, Cy, we may have 

ORO sR OTS ERY 8.97) 2 


and perhaps, as M. Millon has suggested, carbureted hy- 
drogen gas and otto of roses, which have the same con- 
stitution, differ, in the one containing charcoal and the oth- 
er diamond. 

These peculiarities are known under the name of allo- 
tropic states, and the phenomenon itself under the desig- 
nation of allotropism. 


What are metameric bodies? What are polymeric bodies? What is 
meant by the allotropic condition of bodies? What allotropic states does 
carbon present ? How may an allotropic change be impressed on chlorine ? 
What are the allotvopic states of iron? Are these peculiarities continued 
in the compounds % 


164 CHEMICAL AFFINITY. 


. LECTURE XXXVII. 


CuemicaL Arrinity.—Phenomena accompanying Chemi- 
cal Affinity —Disturbance of Temperature.—Production 
of Light—Evolution of Electricity — Change of Color. 
— Change of Form.— Change of Chemical Properties. — 
Change of Volume and Density.— Tables of Geoffroy.— 
Measure of Affinity —Disturbing Causes. 


By chemical affinity we mean the attraction of atoms 
of a dissimilar nature for each other, an attraction which 
is exhibited upon the apparent contact of bodies. 

There are certain striking phenomena which very fre- 
quently accompany chemical action. They are the evo 
lution of Light, Heat, and Electricity; and, as respects 
the bodies engaged, they may exhibit changes of color, of 
form, of volume, of density, or of their chemical proper- 
ties. 

Fig. 143. Tf, in a glass vessel, a (Fig. 143), a mixture of 
7? strong sulphuric acid and water be stirred togeth- 
LHW er by means of a tube, 4, containing some sul- 

72 phuric ether, so much heat will be evolved by 
the acid and water as they unite, that the ether 
9 ~will be made to boil rapidly. 

If, upon some water contained in a shallow dish (Fg. 

Fig.144. 144), a piece of potassium be thrown, the 
{eE® potassium decomposes the water with the 
AZ == evolution of a beautiful lilac flame. 

As respects the evolution of electricity 
during chemical action, the Voltaic battery, 

: > and, indeed, all Voltaic combinations, are ex- 
amples. In the simple circle we have already, in Lec- 
ture XX VIII., traced the production of electricity to the 
decomposition of the water. 

We have observed that the evolution of the imponder- 
able agents is not the only phenomenon to be remarked 
during the play of chemical affinity, the ponderable sub- 
stances themselves undergo changes. 


What is meant by chemical affinity? What phenomena accompany 
chemical action? What changes are exhibited by the ponderable bodies 
themselves? Give examples of the evolution of heat, light, and electricity, 


se 


CHANGES OF COLOR AND FORM. 165 


If, in a glass containing litmus water, a drop of sul- 
phuric acid is poured, the “blue color of the litmus is at 
once changed to a red, and if into the reddened liquid so 
produced a little ammonia is poured, the blue color is 
restored. This simple experiment is of considerable in- 
terest, for the reddening of litmus is commonly received 
as one of the attributes of acid bodies, and the restoration 
of the blue color of those belonging to the alkaline type. 

On adding to a solution of sulphate of copper a small 
quantity of ammonia, a pale green precipitate is thrown 
down ; a greater quantity of ammonia redissolves this pre- 
cipitate, and gives rise to a splendid purple solution. 

A similar solution of sulphate of copper gives rise, un- 
der the action of a solution of ferrocyanide of potassium, 
to a deep chocolate-colored precipitate. 

A. solution of the nitrate of lead, which is colorless, act- 
ed on by a solution of iodide of potassium, also colorless, 
sgives rise to the production of a beautiful yellow precipi- 
tate, the iodide of lead. 

And, lastly, if sulphuric acid be placed in a solution of 
a soluble salt of lead, or of baryta, a white precipitate at 
once goes down. 

These are all instances of changes of color, and such 
changes are of the utmost importance in practical chem- 
istry, imasmuch as the art of testing depends, for the most 
part, upon a knowledge of them. 

Changes of form in the same manner are exhibited ; 
thus, when gunpowder explodes, a large proportion of the 
ingredients, from being in the solid, escapes in the gaseous 
state. If, upon fragments of chalk, carbonate of lime, we 
pour hydrochloric acid, a vidlent effervescence takes place, 
due to the escape of carbonic acid, which, from being in 
the solid, assumes the gaseous form. 

The converse of this is sometimes seen, va- Fis. 145. 
pors passing into the solid state. In the glass, gases 
a (fig. 145), place some strong hydrochloric 
acid, and in 6 some strong ammonia; both these 
bodies yield vapors at ordinary temper. atures in 
abundance, and those vapors meeting in the air 
over the glasses, give rise to a dense fume, or smoke, 
which, if examined, proves to be solid sal ammoniac. 

Give examples of changes of color. On what do the processes of 


testing for the most part depend? Give an example of the production of 
a gas from a solid, and a solid from gases. 


@ 


166 ' CHANGES OF PROPERTIES. 


Fig. 146. 


Very often change of form is accompanied 
by change of color; thus, if under a large bell 
jav (fg. 146) there be placed a wine-glass 
containing a few copper or iron nails and nitric 
acid, a gas of a deep orange color makes its 
appearance, filling the whole bell. 

Perhaps no better mstance of an entire 
change of properties could be cited than that of the com- 
bustion of phosphorus in atmospheric air. This substance 

Fig. 147. phosphorus is a body of a waxy appear- 
“ance, possessing so great a degree of com- 
bustibility that it requires to be kept un- 
der the surface of water to prevent the ac- 
tion of the air. If a piece of it be set on 
fire beneath a clear and dry bell jar, as 
shown in Ig. 147, it unites with great 
energy with the oxygen of the included 
air, producing white flakes, which, as the 
combustion is ceasing, descend in the jar, giving a min- 
iature representation ofa fall of snow. On collecting some 
of this phosphoric snow, its properties will be found to be 
in striking contrast with the phosphorus which produced 
it; for instance, far from being unacted on by water, it 
has such an intense affinity for that substance, that it 
hisses like a red-hot iron when brought in contact with 
it. It reddens litmus solution, and possesses the quali- 
ties of a powerful acid. Nor is the change confined to 
the phosphorus; if we examine the air in which it was 
burned, we find it has lost its quality of supporting com- 
bustion. 

Changes of volume, and, consequently, changes of dens- 
ity, constantly attend chemical action ; a pint of water and 
a pint of sulphuric acid, mixed together, form less than 
two pints; and the same may be observed of alcohol and 
water. . 

When to two substances already in union, a third, hav- 
ing a stronger affinity for one of the other two, is present- 
ed, decomposition ensues. Thus, if to the carbonate of 
soda nitric acid be presented, the soda and nitric acid com- 
bine, and the carbonic acid is driven off in the form of a 


What are the changes which phosphorus undergoes when burned in 
the air? Give an example of change of volume and of density. Under 
what circumstances does decomposition take place ? 


MEASURE OF CHEMICAL AFFINITY. 167 


gas. And, again, if upon the nitrate of soda so produced 
sulphuric acid is poured, the nitric acid is driven off, and 
sulphate of soda results. It was at one time thought that, 
by examining a number of such cases, we might discover 
the order of affinity of bodies.for one another and arrange 
them in tables; these are sometimes called the Tables. of 
Geoffroy. Thus, the table 
Soda. 

Sulphuric acid, 

Nitric 

Muriatic “ 

Acetic v4 

Carbonic “ 
presents us with the order in which a number of acids 
stand in relation to soda, the most powerful being the first 
on the list, and the salt which results from the union of 
any one Ms those acids with the soda can be decomposed 
by the use of any other acid standing higher on the list. ; 

But it is now known that these tables are far from rep- 

resenting the order of affinities; a weaker affinity often 
overcomes a stronger by reason of the intervention of 
disturbing extraneous causes; and tables so constructed 
lead, therefore, to contradictory conclusions. Some very 
simple considerations may illustrate this. Potassium can 
take oxygen from carbon at low temperatures, or, in other 
words, decompose carbonic acid gas, but it by no means 
fellowes that the affinity of potassium for oxygen is great- 
er than that of carbon, and accordingly we find that at 
higher temperatures carbon can take oxygen from potas- 
sium. Indeed, under the influence of heat, light, and 
electricity, we find all kinds of chemical changes going 
on, and in the same manner the condition of form exerts 
a remarkable influence in these respects, so that cohesion 
and elasticity may be placed among the predisposing caus- 
es producing chemical results. Tf a number of bodies 
exist in a solution together, they will at once arrange 
themselves in such a way under the influence of cohesion 
as to produce insoluble precipitates, if that be possible ; 
or, under the influence of elasticity, to determine the evo- 


What are the tables of Geoffroy? How may it be shown that these 
are not tables of affinity? What may be enumerated among these dis- 
turbing causes? What is the influence of cohesion? What is the influ- 
ence of elasticity? Give examples of the action of these disturbing agents. 


168 TABLES OF GEOFFROY. 


lution of a gas; if the carbonate of soda is decomposed 
by acetic acid, it by no means follows that the latter has 
the stronger affinity for soda, the decomposition being 
probably determined by the fact that the carbonic acid 
can take on the elastic form and escape away as a gas. 
The sulphate of soda may be decomposed by baryta, the 
cause of the decomposition being probably due to cohe- 
sion, for the sulphate of baryta which results is a very in- 
soluble body. We have, therefore, no true measure of 
affinity, for the relation of bodies in this respect changes 
with external conditions, and the tables of Geoffroy are 
only tables of the order of decompositions, but not of the 
order of affinity. 


What do the tables of Geoffroy, in reality, express? 


PART III. 


INORGANIC CHEMISTRY. 


LECTURE XXXVIII. 


PNEUMATIC CHEMISTRY.—Ancient Opinions on the Con- 
stitution of the Gases Doctrine of the Unity of Ar. 
Oxyern Gas.— Modes of Preparation.—Properties.— Orr- 
gin of its Name.— Relations to Atmospheric Air and 

Combustion.— Burning of Metals. 


In the catalogue of the elementary bodies of the an- 
cients four substances were included, earth, air, fire, and 
water. The progress of knowledge has shown that three 
out of the four are compound bodies. 

For a length of time it was supposed that the various 
exhalations and vapors were nothing more than vitiated. 
forms of atmospheric air; and though from time to time 
first one and then another of the gaseous bodies was dis- 
covered, chemists were slow to admit that they were any 
thing more than modifications of one common principle. 
Thus, Roger Bacon, in the thirteenth century, discovered 
one of the carburets of hydrogen, and Van Helmont, in 
the sixteenth, carbonic acid. The invisibility of these 
bodies, their remarkable chemical relations in extinguish- 
ing flame and producing death, the great mechanical force 
to which they often gave rise when generated in pent-up 
vessels, their occurrence in mines, the bottom of wells, in 
church-yards, and lonely places, suggested to a supersti- 
tious mind a supernatural origin, and Van Helmont gave 
them the name of gas, corrupted from gahst (or geist), 
which signifies a ghost or spirit. 

But it is to the researches on the properties of fixed air, 
which Black made about 1750, that pneumatic chemistry 
owes its origin. These were soon followed by the dis- 
coveries of Priestley, Scheele, and others. That of oxygen 

What opinions were formerly held respecting the different gases? 


What was the original signification of the term gas? By whom was the 
doctrine of the plurality of airs established ? 


170 PREPARATION OF OXYGEN. 


gas, by the former of these philosophers, in 1784, forever 
destroyed the ancient notion of vitiated airs; for this gas 
can support combustion and respiration far better than the 
atmosphere. It may be said with justice that modern 
chemistry dates its origin from the discovery of oxygen gas. 


OXYGEN. O=8°013. 


Oxygen gas is probably the most abundant of the ele- 
ments. It constitutes about one third of thé weight of the 
solid mass of the earth, eight ninths of that of the waters 
of the sea, and one fifth the volume of the air. 

A simple mode of preparing oxygen is to place ina re 


6 et 


SI ! iM aibeaboezs met E> 


tort, a, Fig. 148, some red oxide of mercury, connecting 
with the retort a receiver, 6, from which there passes a 
bent tube, c, which dips beneath the water of a pneumatic 
trough, g. On raising the temperature of the oxide by 
the flame of a spirit lamp, it is resolved into metallic mer- 
cury and oxygen gas; the former distills into the receiver 4, 
and the latter collects in the inverted jar of the trough. 

Another process is to place the peroxide of manganese 
(Mn. O,) in an iron bottle, from which a tube, 4, Fug. 149, 
projects; this tube may be connected with another, f, by 
means of a cork and an India-rubber tube, e. The bot- 
tle is to be arranged in a small furnace, and made red hot; 
the manganese loses one third of its oxygen, which may 
be collected in a gas-holder, as shown in the figure. 

The most convenient mode of preparing it is to place in 
a flask, a, Fig. 150, a mixture of chlorate of potash and 
peroxide of manganese; to the mouth of the flask a tube, 


6, is adapted by means of a tight cork, the lower end of the 


In what bodies does oxygen occur? Describe its preparation from red 
oxide of mercury, from peroxide of manganese, and from chlorate of potash. 


r PREPARATION oF OXYGEN. 171 


Fig. 149. 


a ee oe 
a es an 
1 
i} 


en ii ih 


In 


Pi 


tube dipping beneath a jar upon 
the pneumatic trough, ¢. On rais- 
ing the temperature of the flask by 
a spirit lamp, oxygen gas is freely 
evolved. ‘I'he peroxide of manga- 
nese takes no_part in the change, 
but it causes fe decomposition - to j 
go on at a low temperature, and the gas is more rapidly 
set free. The change, being confined to the chlorate of 
potash, is therefore expressed as follows : 


EOr-y CL Os co ede Che Og: 


that is, the chlorate of potash, at the temperature in ques- 
tion, has its atoms disarranged, resolving itself into one 
atom of chloride of potassium and six atoms of oxygen gas. 

It may also be prepared by exposing a mixture of bi- 
chromate of potash and sulphuric acid, or peroxide of 
manganese and sulphuric acid, to heat. 

Oxygen gas is a colorless body, having no odor nor 
taste. It is a non-conductor of electricity, and a bad re- 
fractor of light. It is a powerfully electro-negative ele- 
ment. In specific gravity it is heavier than atmospheric 
air; for the air being 1-000, oxygen is 1:1026, or, accord- 
ing to some chemists, 1°1111. One hundred cubic inches 
weigh about 34 grains. Its atomic weight. is 8013, hy- 


What are its leading physical properties? What is its specific gravity? 


172 PROPERTIES OF OXYGEN. 


drogen being taken as 1:000. It has never been con- 
Honeed into the liquid state. 

To a certain extent it is soluble in water, one hundred 
volumes of that liquid dissolving about four of the gas, a 
fact of considerable importance in physiology, as it is upon 
the oxygen so found in water that aquatic animals depend 
for their respiratory process. 

On litmus water, or any blue vegetable solution, oxy- 
Fig. 151. gen exerts no action, as is easily shown by agita- 
ting it with such a sonuOn in Hope’s eudiometer 
(fig. 151); but though it is not acid itself, when 
it unites with a oreat variety of bodies it gives 
rise to powerful acids, and from this circumstance 
its name was derived. Oxygen, oévc, acid, and 
YVEVVELY, to generate. 
| The most important qualities of atmospheric air 
are fue to the presence of oxygen gas. It is for this reas- 
on that the air supports combustion and respiration. The 
powers of oxygen, in this respect, may be illustrated by 
many striking experiments ; thus, if into a jar filled with 
Fig. 152. it, a stick of wood, with a spark of fire on its ex- 
tremity, be ja eetect it bursts out at once into a 
flame, burning br illiantly. 

On immersing a lighted taper in a jar of oxygen 

(Fig. 152), hs, light becomes of a dazzling white- 
' ness, the taper wasting rapidly away ; but it is to 
be observed that after a time the combustion de- 
clines, and finally the light is extinguished. 

If a piece of charcoal of bark in an ignited state be 
Fig. a placed in a bottle of oxygen, the combustion 
« Uy goes on with great activity, a multitude of 
AN) \ barks being thrown off. When the char- 
<a a) ) coal is extinguished, if a little lime-water be 
’ poured into the bottle and agitated in it, the 
dx lime-water at once becomes of a milky white- 
_ ness; for the carbon, during the combustion, uniting with 
the oxygen, produces carbonic acid gas, and this forms 
with lime a white insoluble precipitate, the carbonate of 
lime. 


Can it be liquefied? Is it soluble in water? From what circumstance 
is its name derived? What are its relations in the ordinary processes of 
combustion? Describe its effect on a lighted taper, and on ignited char- 
coal, 


COMBUSTION IN OXYGEN. . 173 


A piece of India-rubber set on fire, and immersed in 
oxygen gas, burns with the emission of a daz- rig. 154. 


zling light. And if, upon a small stand, some 
burning sulphur is placed, and a jar of oxygen 
inverted over it, as shown in J%g. 154, the 
light which is emitted is of a splendid blue 
color, and the smoke ascending up the middle 
of the jar, and falling in curious rings down 
its sides, affords an illustration of the. manner 
in which currents are excited in gases. 


But it is not alone such substances as wood, char- 
coal, or sulphur which will burn in oxygen gas; Fig. 155. 


many bodies commonly regarded as incombust (aie 
give rise to the same result. If a piece of steel 
wire be rolled round into a spiral, and the ex- 
tremity of it be dipped in melted sulphur, or 
wrapped round with cotton, so as to afford the 


means of introducing it in an ignited condition | 
Fig. 156. 


into oxygen gas, the 
combustion is at once commu- 
nicated to the steel, which 
burns in a very brilliant man- 
ner, emitting scintillations. 

A stream of oxygen from a 
gas-holder, being thrown upon 
an iron nail made red hot in 
the flame of a spirit lamp, or 
placed in an ignited cavity in: 
a plece of charcoal, causes the 
iron to burn with rapidity, 
emitting a shower of sparks. 


What is its effect on ignited sulphur? What is its effect on an ignited 


metal, as iron or steel? 


P2 


174 COMBUSTION IN OXYGEN. 


LECTURE XXIX. 


OxyGEN contTINUED.—Drummond’s Light.— Combustion of 
Phosphorus.— Double Change arising in Combustion.— 
The Lavoisierian Doctrine.— Basic, Indifferent, and 
Acid Oxides.—Physiological Relations of Oxygen.— 
Supporters of Combustion.—Nature of Flame—Con- 
stancy of Heat evolved.—Vegetable Origin of Oxygen 
in the Aur. 


Ir a piece of lime the size of a peppercorn be placed 
in the flame of a spirit lamp, through which oxygen gas 
is directed by a blowpipe, the lime phosphoresces pow- 
erfully, emitting a light so bright that the eye can scarcely 
bear it. Thisis the original form of what is called Drum- 
mond’s light. The light, however, is still brighter when 
the oxyhydrogen blowpipe is employed. 

he combustion of phosphorus in oxy- 
gen gas constitutes one of the most brill- 
iantexperiments. A piece of lighted phos- 
phorus immersed in an atmosphere of this 
gas, burns with the evolution of a prodig- 
ious amount of light and heat, Fug. 157. 
Notwithstanding the production of dense 
flakes of phosphoric acid intervening be- 
tween the eye and the burning mass, the 
light is very brilliant. 

When any combustible substance is burned in oxygen 
gas, two striking phenomena are exhibited: a change in 
the combustible, and a change in the oxygen. A fragment 
of ignited charcoal rapidly wastes away, and the surround- 
ing gas loses its power of supporting combustion. Until 
the time of Lavoisier, it was generally supposed that burn- 
ing was due to the escape of a certain principle, called 
phlogiston, from bodies, but he showed that in all these 
cases there is no loss of weight, and that, in reality, the 


What is the original form of the Drummond light? What are the phe- 
nomena of the combustion of phosphorus in oxygen? In these combus- 
tions, what changes take place in the oxygen and in the burning body ? 


THE OXIDES. 175 


combustion is due to the oxygen uniting with the burning 
body; and if care be taken to collect all the products of 
the action, their united weight will be exactly that of the 
oxygen and combustible conjointly. Lavoisier was dis- 
posed to believe, that in all cases of true burning the pres- 
ence of oxygen is indispensable, an idea now known to 
be erroneous; for light and heat are evolved in all cases 
where chemical action is going on with great intensity, 
no matter what may be the substances which happen to 
be present. 

In the Lavoisierian system of chemistry, oxygen was 
regarded as being the essential supporter of combustion ; 
and as, in many instances, it gives rise to the production 
of acids, it was also regarded as the essential principle of 
acidity ; and from this circumstance its name was derived, 
as has been already said. But so far from every acid 
containing oxygen gas, it is now well known that there 
are many from which this principle is wholly absent. If 
any substance in particular deserves the name of “ the 
acid former,” it is hydrogen, for it is doubtful whether 
any powerful acid exists which does not contain hydro- 
gen. Basic substances, on the contrary, are characterized 
by containing oxygen. | | 

To the compounds which arise from the union of oxy- 
gen with other bodies the generic designation of oxides 
is given; and of them we have three classes. Ist. Basic 
oxides. 2d. Indifferent oxides. 3d..Acids. If M repre- 
sents an electro-positive body, the basic oxides are con- 
stituted as follows: 


MOeT*: : .  Protoxide, usually the most powerful base. 
M,O;. , : Sesquioxide, a weaker base. 

116 ae i s Deutoxide, a still weaker base. 

M,O . : : Suboxide, - ts 


The oxides of manganese furnish a good example of 
the three classes : 


Protoxide of manganese . ‘ MnO. . : 
Sesquioxide i : : Mn, O; : Basic oxides. 
Deutoxide . J é : : MnO, Indifferent oxide. 
Manganic acid . ; : d MnO, Acid 
Hypermanganic acid . : ¢ MnO; sigs 


What was Lavoisier’s theory of combustion? What is the relation of 
oxygen to acid and basic bodies? What is the generic designation for its 
compounds ? What are the three classes of compounds which it yields ? 
In the basic, the indifferent, and the acid group, what is the general rela~ 
tion of the oxygen? 


176 PHYSIOLOGICAL RELATIONS OF OXYGEN. 


From which it may be inferred that, in a family of ox- 
ides of an electro-positive body, the most powerful base is 
that containing one atom of oxygen, and that, as the quan- 
tity of this element i increases, indifferent bodies may be 
formed ; that is to say, those in which neither the basic 
nor acid qualities are well marked, and on a still farther 
increase acids are produced. In this respect, therefore, 
the original idea of Lavoisier respecting the character of 
oxygen is to some extent substantiated. 

In its physiological relations oxygen 1S a most interest- 
ing body. It is for the purpose of introducing this ele- 
ment to the interior of the system that the respiratory 
mechanism of animals is devoted—a mechanism which 
differs according to their mode of life, the gills of a fish 
and the lungs of a man having the same ulterior object. 
If two jars are taken, one full of atmospheric air, and one 
of oxygen gas, and small animals placed beneath each, it 
will be found that in the latter those animals survive 
much longer than in the former. The gas introduced 
into the system arterializes the blood, and, eventually unit- 
ing with carbon and hydrogen, keeps up the temperature 
to a standard point, which, in the human mechanism, is 
about 98° F. Oxygen gas, therefore, is emphatically the 
supporter of respiration. 

The terms, supporter of combustion and combustible 
body, formerly much used by chemical writers, are ex- 
pressive of an erroneous idea. No substance is in itself 
a supporter of combustion, nor is any one intrinsically a 
combustible body. If a jet of hydrogen burns in an at- 
mosphere of oxygen, so, also, will a jet of oxygen burn in 
an atmosphere of hydrogen gas. In fact, both bodies are 
equally engaged in producing the result, combustion only 
taking place upon their mutual surface of contact. The 
division in question has arisen from the circumstance that 
the most familiar instances of combustion we witness 
take place in the atmosphere, which owes all its active 
qualities to the presence of oxygen. 

Combustion takes place only at those points where the 
uniting substances are in contact. ‘The flame of a can- 


For what purpose is oxygen introduced into the system? Why is it to 
be regarded as the supporter of respiration? Is the division of bodies into 
combustibles and supporters of combustion a correct: one? What is the 
nature of flame ? > 


STRUCTURE OF FLAME. ey fT. 


dle is not incandescent throughout, but is a Fig. 158. 
mere superficies or luminous shell, with a dark i 
interior. In such a flame several distinct parts 
may be traced. Around the wick, a, Fig. 158, 
at the points 22, the light is of a Sees ‘Goldes (oe 
here the air being in excess, the combustion is 
perfect. From this toward ¢ the combustible 
matter predominates, and the light is most in- 
tense. A faint exterior.cone, e e, surrounds the 
more luminous portion, but the interior at 0 is 
totally dark, as may be proved by placing a 
piece of mica or glass upon the flame. It is prob- : 
able that the light arises chiefly from the ignition of ed 
matter, for incandescent gases are only faintly luminous. 
The hydrogen of the flame is first burned, and for a mo- 
ment carbon is set free in the solid form at a very high 
temperature, its oxydation instantly ensuing. 

A given weight of a combustible body, when burned, will 
always furnish a constant amount of heat. If an ounce of 
carbon be burned in a few moments in pure oxygen gas, 
the amount of heat disengaged appears to be very great ; 
though, in reality, it is the same that would finally be yield- 
ed by a slower combustion in atmospheric air. So, too, me- 
tallic iron becomes white hot when burned in oxygen, be- 
cause the combination goes forward with great rapidity ; 
but precisely the same amount would be yielded in the slow 
oxydation of rusting, though in the latter instance it might 
take years for the completion of the process. This is a 
fact of great physiological importance. 

We have just said that atmospheric air owes all its ac- 
tivity to the presence of oxygen, and as there are inces- 
santly combustive processes going on, the tendency of 
which is to remove oxygen from the air and generally re- 
place it with carbonic acid—a result, also, which ensues 
from respiration, in every part of the earth where animals 
are found—it would appear a necessary consequence that 
the constitution of the air should incessantly change, the 
amount of oxygen declining and that of carbonic acid in- 
creasing. But in this respect the vegetable world exerts 


Why do the different regions of a lamp flame differ in luminous power? 
Is there any difference in the amount 'of heat evolved in rapid and in slow 
combustions? What are the causes which tend to diminish the amount 
of oxygen in the air? 


178 ORIGIN OF OXYGEN IN NATURE. 


an opposite tendency to the animal; for, under the influ- 
ence of the light of the sun, plants decompose carbonic 
acid gas, setting free its oxygen, and appropriating the 
carbon to their own uses. This beautiful fact was origin- 
ally discovered by Priestley, who found, that if some green 
Fig. 159. leaves were placed in a bottle, as in Fug. 159, con- 
2» taining carbonic acid gas, or, what is more conven- 
7 ient, water holding that substance in solution, so 
long as the sun does not shine on them no action is 
perceived ; but if the bottle be set in the sun, bub- 
bles of gas are rapidly disengaged from the leaves, 
and, rising up through the water, collect in the upper 
part of the bottle, and, if examined, prove to be very rich 
in oxygen. 

A question has arisen as to what principle the remark- 
able decomposition is due. I have proved, by causing it 
to take place in the prismatic spectrum, that it is due to 
the yellow ray of light—(Phil. Mag., Sept., 1843.) 


LECTURE XL. 


Hyprogen.—Preparation and Properties of Hydrogen.— 
Relations to Respiration. Combustibility —Its Light- 
ness.—Haplosive Combustion.— Production of Water.— 
Oxyhydrogen Blow-pipe. 

HYDROGEN. H=1. 

Ir a piece of potassium be wrapped in paper and rap- 
idly immersed beneath an inverted jar at the water-trough, 
violent reaction soon sets in, a gas collects in the upper 
part of the jar, and the potassium, oxydizing, dissolves in 
the water. The gas so produced is hydrogen, and the 
decomposition is very simple, as shown in the following 
symbols : 

HO Tat WhO ay 

that is, water acted upon by metallic potassium yields ox- 

ide of potassium and hydrogen gas. 

In practice more economical processes are resorted to. 
Like potassium, metallic zinc can decompose water at or- 
dinary temperatures, but there is this difference between 


By what agency is this tendency compensated 1 ? What is the principle 
of the decomposition of water by potassium ? 


HYDROGEN GAS. 179 


them, that while the oxide of potassium is very soluble in 
water, the oxide of zinc is nearly insoluble. <A plate of 
polished zine immersed in water does not, therefore, give 
rise to a stream of gas, for the moment the incipient ac- 
tion has set in it ceases, the zinc becoming covered with 
an impervious pellicle of oxide, which cuts off farther 
contact with the water. 

If, however, we add any acid substance which can form 
with the oxide a salt soluble in water, the action will go 
on continuously, because the zinc can now expose a clear 
metallic contact. Such a substance is sulphuric acid. To 
make hydrogen, therefore, we take a bottle, 
a, Fig. 160, and having placed in it some 
strips of zinc, add sufficient water to cover b 
them entirely, and then adjust to the mouth jm 
of the bottle a cork, through which two tubes, 
6 and c, pass. Through 6 sulphuric acid is 
poured in such a quantity as to excite a brisk { 
but not too violent effervescence, and the gas, Wi 
as it generates, passes out throughe. It is absolutely nec- 
essary to allow a quantity of the gas to escape before at- 
tempting to collect it, because the first portions form, with 
the air in the upper part of the bottle, an explosive mix- 
ture; but as soon as itis judged that the air is all expelled, 
we may proceed to collect the gas; and whenever the pro- 
duction slackens, if more acid be added through the fun- 
nel tube, 6, the supply may be kept up. 

Hydrogen gas is a transparent and colorless body, 
which exerts a powerful refracting action on light. When 
pure, it has neither taste nor smell, but, as thus obtained, 
ithas a peculiar odor. It is the lightest body in nature, its 
specific gravity being 0:0694. One hundred cubic inches 
of it weigh 2°1 grains. The weight of its atom is taken 
as the standard of comparison of other atomic weights in 
this book; it is therefore = 1. It exerts no action on 
vegetable colors, and is very sparingly soluble in water, 
one hundred cubic inches of that liquid dissolving about 
one and a half of hydrogen gas. Hydrogen has never 
been liquefied. 

As respects the animal economy, hydrogen gas does 


(= 


What is the reason that zinc can not decompose water alone? How 
may hydrogen gas be made by the aid of zinc? What are the properties 
of this gas? 


180 PROPERTIES OF HYDROGEN. 


not exert any directly deleterious effect ; and although it 
can not, of course, carry on the functions of respiration, 
which are acts of oxydation, yet it can, for a short space, 
be introduced into the lungs with impunity. Ifa person 
whose lungs are inflated with it attempts to speak, his 
voice resembles the feeble and shrill voice of a child. 
This arises from the small density of hydrogen; a bell 
rung in this gas emits almost as feeble a sound as if rung 
in a vacuum. 

One of:the most striking peculiarities of hydrogen is its 
great inflammability in contact with ox- Fig. 161. 
ygen. Ifa jar, Pg. 161, with a stop- 
cock at its upper extremity, be filled 
with hydrogen, and then, being depress- 
ed in the water of the trough, the cock 
opened and a light brought near the 
Figo. hydrogen as it escapes, it takes = 

fire at once, burning with a pale - 

yellow flame. Orif tothe mouth 

of a bottle containing the mate- 

rials for generating hydrogen, a, Fig. 162, a cork, 
% through which a glass tube, 4, is passed, be adjust- 

ed, and after allowing the air in the bottle to be dis- 

placed, a lightbe applied to the issuing gas, it takes 
fire and burns in the same manner; an experiment com- 
monly described as the philosophical candle. 

The following experiment proves three facts at the 
same time: 1. The great lightness of hydro- 
gen; 2. Its inflammability; 3. That it is not a 
supporter of combustion. A jar, a, Fig. 163, is 
to be filled with hydrogen at the water-trough, 
and then, being lifted in the air with its mouth 
downward, a taper, placed on a bent wire, is car- 
: ried into its interior. As the taper passes the 
mouth of the jar there is a feeble explosion, and the hy- 
drogen taking fire, burns with a pale flame; but as soon 
as it is immersed in the atmosphere of the gas the taper 
is extinguished. It may, however, be relighted as it is 
brought out of the jar at the burning hydrogen, and this 
may be repeated several times in succession. The com- 


What are its relations to respiration? How may its combustibility be 
demonstrated? How may its inflammability, its non-supporting power, 
and its lightness be simultaneously illustrated ? 


COMBUSTION OF HYDROGEN. 18] 


bustibility of the gas and its quality of not supporting 
combustion are obvious enough, and its lightness is proved 
by the fact that it does not flow out of the open mouth of 
the jar, which it would do at once if it were heavier than 
atmospheric air. 

The application of hydrogen to aerostatic purposes is 
founded upon its small specific gravity. This property is 
very distinctly illustrated by filling an India rubber gas- 
bag with hydrogen, and having attached to the stop-cock,a, 
Fig.164, which closes it, a common earth- Fig. 164. 
en-ware tobacco-pipe, 4, by dipping the 
pipe ina Suen of soap, bubbles may 
be blown. These rise through the air 
with rapidity ; and if a lighted taper is 

5 , 
brought near them as they are ascending, 3/~ 
the hydrogen takes fire and burns witha © 
yellowish flame. 

If, in a strong brass vessel, a, Fig.165, we place a mixture 
of hydrogen and atmospheric air in equal Fig. 165. 
volumes, and, having inserted the cork, c, ¢ 
tightly, pass, by the aid of the ball and 
wire, 0, an electric spark through the gas, 
a violent explosion takes place, the hydrogen burning in- 
stantaneously with the atmospheric oxygen, and giving 
rise to the production of water. 

Musical sounds originate in vibratory movements com- 
municated to the air. If the flame of a philosophical can- 
dle is covered by a wide glass tube, as, for example, Fig. 166. 
the neck of a broken retort, an intensely powerful f 
sound is emitted. This arises from the circum- 
stance that the hydrogen burns in the tube, giving 
rise to a series of small explosions, which follow 
each other with rapidity, and these explosions throw 
the air in the tube into a vibratory state. Accord- 
ing as the tube is raised or lowered, these explo- 
sions occur with different degrees of rapidity, some- 
times producing a clattering sound, and then a pure mu- 
sical note. 

Whatever may be the circumstances under which hy- 


To what purpose is hydrogen applied in consequence of its lightness ? 
How may this be illustrated on a small scale? When mixed with oxygen 
or air, and an electric spark passed through it, what is the result? Under 
what circumstances will the flame of hydrogen emit a musical sound ? 


182 OXYHYDROGEN BLOW-PIPE. 


drogen burns, whether quietly, as in the philosophical 
candle, or with trivial explosions, as in this tube, or with 
a violent detonation, as in the preceding experiment, the 
uniform product of the combustion is water. During the 
combination of these elementary bodies with each other a 
very great amount of heat is given out, for hydrogen 
combines with eight times its own weight of oxygen, a 
greater proportion than is met with in the case of any 
substance whatever. Advantage is taken of this in the 
construction of the oxyhydrogen blow-pipe, an instrument 
invented by Dr. Hare, which furnishes us with the most 
efficient means of obtaining a high temperature. There 
Fig. 167. are several different forms of this blow- 
a) pipe; in some the gases are mixed in the 
A proper proportions in a strong receiver, 
and set on fire after passing through a 
Hemming’s safety tube. But it is better 
to keep them in separate reservoirs, and 
conduct them to a common jet, where 
3 they may simultaneously mix and be 
burned, as is shown in Fug. 167, where O is the oxygen 
reservoir, H the hydrogen, a 6 the flexible lead pipes, 
leading to a common jet, c, at which the gases are set on 
fire. By this instrument substances perfectly infusible 
in a common furnace melt at once. The intensity of the 
heat of this blow-pipe depends, to a great extent, on the 
fact that, unlike ordinary flames, the oxyhydrogen flame 
is, aS it were, solid; that is, mcandescent throughout all 
its parts. 

In its general relations, hydrogen possesses so many of 
the properties of the metallic class, that there is every 
reason to believe it is, in reality, a metal. The facts of 
its aerial form and transparency can scarcely be regard- 
ed as of any weight against this conclusion, for the vapor 
of mercury possesses a similar aspect. 


What is the uniform production of its combustion? Why is so much 
heat evolved in the burning of a mixture of oxygen and hydrogen? De- 
scribe Hare’s compound blow-pipe. What is the peculiarity of the flame? 
To what class of bodies does hydrogen probably belong ? 


WATER. 183 


LECTURE XLI. 


Warer.— Hydrogen Acids.— Water.— Its Properties. — 
Compressibility.— Constitution of Water —Syntheses of 
Water—By Spongy Platinum.—Determination of rts 
Composition by Weight.—Analysis of Water — Chemi- 
cal Relations of Water.— Water of Crystallization and 
Saline Water.—Acts as a basic, indifferent, and acid 
Body. —Purification.— Deutoxide of Hydrogen. 

WATER. HO=9-013. 

Hyproeen unites with all the electro-negative substan- 
ces, and, with many of the more prominent ones, forms 
strong acids. The hydrogen acids of chlorine, bromine, 
iodine, and fluorine are all constituted upon the same 
type, in which, if the electro-negative radical be repre- 
sented by &, we have 

va ie 


But with oxygen, instead of an acid, a neutral body re- 
sults. This body is common water. 

Water, as will be presently proved, results from the 
union of oxygen and hydrogen, one atom of each of these 
elements combining to form one atom of water. It is, 
therefore, a binary compound. Its symbol is 


Ve hos 


By volume, it consists of two of hydrogen united with 
one of oxygen; by weight, one part of oxygen united 
with eight of hydrogen. These statements correspond 
with the first, because the hydrogen atom is twice the 
volume of that of oxygen; and the weight of an atom of 
oxygen is eight times that of hydrogen. 

Water is a colorless and tasteless body. It freezes at 
32° F., and boils at 212° F. Its specific gravity is 1-000, 
being the standard of comparison of all other liquid and 
solid bodies. The specific gravity of its vapor, steam, 
compared with atmospheric air, is 0°6201. It is a com- 
pressible and elastic substance. One cubic inch of it at 
62° weighs 252°45 grains. 

When hydrogen unites with electro-negative substances, what class of 


bodies arise? What is the constitution of water? What are the proper- 
ties of water? 


184 COMPRESSIBILITY OF WATER. 


Fig. 168. The compressibility of water is at once dem- 
onstrated and measured by an instrument in- 
vented by Cirsted, and represented in Fug. 168. 
It consists essentially of a strong glass cylinder, 
a a, filled with water, upon which a powerful 
pressure can be exerted by means of a piston 
driven by a screw, 6. In this cylinder of water 
a gage, represented on a larger scale by fg. 
169,1is placed. The gage consists of a reservoir, 
e, prolonged into a fine tube, f; there is also a 
scale annexed. The reservoir and part ,, 7.169. 
of the tube are filled with water, and a 
small column of quicksilver, 2, indicates 
the point on the tube to which the water 
reaches. ‘The pressure exerted is measured by an 
air-gage, d. 

If, now, this instrument be placed in the strong 
glass cylinder, as seen in Fug. 168, and pressure 
exerted by turning the screw, the air in the gage, 
d, contracts and indicates the amount of that press- 
ure; at the same time, the small column of mercury, 
x, descends in the tube, showing that the water con- 
tracts, and measuring its amount. On turning the 
screw the other way, so as to relieve the apparatus 
of pressure, the air-gage comes back to its original 
point, and the mercury in the fine tube ascends again. 
It is obvious, therefore, that by this instrument we meas- 
ure the compressibility of the water contained in the res- 
ervoir, e, without distending that reservoir, or in any man- 
ner altering its dimensions; for a little reflection will 
Fig.170. show that it is pressed upon equally on the in- 
». side and outside, and therefore its dimensions are 
invariable. Cirsted’s instrument shows that water 
is compressed 55.455 part of its volume for each 
atmosphere of pressure. 

The constitution of water was first clearly proved 
by Mr. Cavendish. It can be illustrated in a vari- 
ety of ways. Thus, if over a jet of burning hydro- 
gen a cold glass bell be suspended, as in Fig. 170, 
it becomes soon covered with a misty dew, and, 


Describe Grsted’s instrument for proving its compressibility. What is 
the amount of its compressibility? How may its composition be synthet- 
ically illustrated ? 


SYNTHESIS OF WATER. 185 


if the experiment be prolonged, drops of liquid finally 
trickle down the sides, and may be caught in a vessel 
placed to receive them. When examined, this liquid is 
found to be water. It has arisen from the union of the 
hydrogen with atmospheric oxygen. 

If in a vessel over the mercurial trough twenty meas- 
ures of pure hydrogen are added to ten measures of pure 
oxygen, and a small pellet of spongy platinurn passed up 
through the quicksilver, union between the two gases 
rapidly takes place, so that it is usual, in order to moder- 
ate its action, to mix the spongy platina previously with 
a little pipe clay. As the gases unite, the mercury rises, 
until at last they have totally disappeared. This beauti- 
ful experiment shows that the constitution of water by 
volume is 2 hydrogen to 1 oxygen, as has already been 
said. 

The composition of water by weight was determined 
by Berzelius as follows: Let a flask, a, Ig. 171, con- 

Fig. 171. 


taining zinc and dilute sulphuric acid, be connected by a 
bent tube, 6, with another tube, d, containing chloride of 
calcium; the hydrogen which is consequently evolved 
from the flask deposits any small quantity of water it may 
be contaminated with in the bulbs ¢ c, and then passing 
through the chloride of calcium tube, d, is made perfectly 
dry. The tube d is connected with a tube of hard glass, 
on which a bulb, e, is blown. This bulb is filled with a 
known weight of oxide of copper, which can be raised to 
a red heat by means of a spirit lamp, 2; and as the dry 
hydrogen passes over the ignited oxide it reduces it, form- 

How may the constitution of water be proved synthetically by spongy 


platinum? Describe the method of Berzelius for determining the compo- 
sition of water by weight. Q 
2 


186 ANALYSIS OF WATER. 


ing with its oxygen water, and leaving pure metallic cop- 
per. The water thus produced is partially collected in 
the bulb f, and the rest of it is detained by a second chlo- 
ride of calcium tube, g. 

If, therefore, we weigh the tube e before and after the 
experiment, in the latter instance its weight will be less 
‘an the former, the difference being due to the amount 

oxygen which has been removed. If, also, we weigh 
the tubes f and g before and after the experiment, in the 
latter case they weigh more than in the former, the differ- 
ence being the weight of the water produced. Thus, it 
will be found that for every eight grains that the oxide 
of copper has lost nine grains of water have been pro- 
duced, showing that the constitution of water is by weight 
8 of oxygen to 1 of hydrogen. 

Fig. 172. The composition of water may also be 
proved analytically as well as synthetically. 
It has been already stated that this can be 
done by the Voltaic battery in a very sat- 
isfactory manner. An apparatus suited for 
this purpose is shown in fvg. 172. The 
polar wires of the battery enter the sides 
of a globular glass vessel full of water, and 
over their terminations tubes are inverted 
== in which to receive the gases. The hy- 
drogen is double the volume of the ox- 

gen. 

Another form of the same apparatus 
is seen in J/g. 173. In a bent tube 
full of water, the platina wires, N P, 
are introduced by means of corks. On 
the current passing, oxygen is collected 
in one of the branches of the tube and 
hydrogen in the other. 

Lavoisier determined the composition 

as, of water by passing its vapor over pieces 

= Of iron made red hot in atube. Thus, 

if from the retort, a, Fig. 174, containing boiling water, 

steam is passed through a red-hot iron tube, ¢ c, filled 

with turnings of iron, or iron wire, decomposition takes 

place, black oxide of iron forming, and hydrogen gas 
escaping by the tube, /, into the gas-holder, m x. 


How may the analysis of water be effected ? Describe the principle of 
Lavoisier’s analysis of water. 


DECOMPOSITION OF WATER. 187 


SSS iiss = MM ae 


rt TTT TMT TTT HTT Ys 


“emt 4 


Te ae 


i HTT 


The chemical relations of water are of the utmost im- 
portance. It exerts a more general solvent action than 
any other liquid known, holding in solution gaseous and 
solid substances, acids, alkalies, and salts. As respects 
gaseous bodies, the quantity which water will take up is 
to a considerable extent dependent on pressure, and in 
the case of salts, an increase of temperature very fre- 
quently increases its solvent powers. Salt-crystals some- 
times contain a very considerable quantity of it, as is shown 
in the case of common alum, of which, if a Fig. 175. 
mass be put upon a red-hot brick, Fug. 175, 5 
it melts in its own water of crystallization, and, 
after a great quantity of steam is thrown off, 
a dry residue remains. Crystals often con- 
tain water in two different states, one portion 
known under the name of water of crystallization, which 
may generally be expelled by a moderate heat; another 
portion known as saline water, which is with much more 
difficulty driven off. In the works on chemistry, the for- 
mul are constructed so as to indicate these different con- 
ditions of the water: Ag (aqua) being the symbol for the 
water of crystallization, and HO for the saline water; thus, 


FeO + SO,+ HO + 64g, 
How does water compare with other bodies as respects solvent power ? 


What is meant by water of crystallization, and saline ‘water? How is 
this difference indicated in formula ? 


188 DEUTOXIDE OF HYDROGEN. 


is the symbol for green vitriol, which is therefore a sul- 
phate of the protoxide of iron, with one atom of saline 
water and six of water of crystallization. The latter is 
easily driven off by heat, but the former only at high tem- 
peratures, or by being replaced by some other body. 

Water unites with many acids with great energy. If 
mixed with sulphuric acid, and a thermometer immersed, 
the temperature will run up rapidly to above 212°. With 
basic bodies, the same results may be obtained as when 
quicklime is sprinkled with water, or potash and soda 
dissolved in it: toward acids water acts as a base; toward 
bases it acts as an acid; and toward salts as an indifferent 
body. 

As found in nature, water is always impure. Rain- 
water and melted snow contain the various soluble gases 
which are in the air; spring, river, well, and mineral 
waters the soluble bodies of the strata through which they 
have flowed; from these it can only be purified by the 
process of distillation. 


DEUTOXIDE OF HYDROGEN. HO2=17°013. 

There is another compound of hydrogen and oxygen, 
the deutoxide ofhydrogen. It contains twice the amount of 
oxygen found in water, and is characterized by a remark- 
able facility of decomposition. It is a liquid substance, 
possesses bleaching powers, and is heavier than water 


LECTURE XLII. 


Nitrocen.—Preparation of Nitrogen.—Properties.—LIts 
Indifferent Nature.—Its Oxygen Compounds.—Atmos- 
pheric Air.— Constitution of—Dimensions of —Rela- 
tions to Organization.— Density and Temperature.—Fix- 
ed and Variable Constituents —Experimental Proofs of 
its Pressure. 


NITROGEN. N=14'19. 


NITROGEN gas is most readily procured from the atmos- 
pheric air by burning phosphorus in a bell jar over the 


What is the relation of water to acids, bases, and salts? By what pro- 
cess is water purified? What is the constitution and properties of the 
deutoxide of hydrogen? What is the process for preparing nitrogen by 
phosphorus ? 


NITROGEN GAS. 189 


pneumatic trough. If a piece 
of phosphorus be laid in a cup 
(Fig. 176) and set on fire, all 
the oxygen in the air of the jar, 
a, willbe consumed, white flakes 
of phosphoric acid forming, and 
these, being finally culvedi in 
the water of the trough, d, there 
is left behind nitrogen, contami- 
nated to a small extent by the 
vapor of phosphorus. 

If nitrate of ammonia be placed i in aretort, and the tem- 
perature raised until it emits protoxide of nitrogen, and 
at that moment, by means of a wire passing through a 
cork in the tubulure, a piece of zinc is lowered down upon 
the melted mass, oxide of zinc is produced, and nitrogen 
gas escapes. The decomposition is very simple, 


INO ..Zn— Zn OO. N. 


Nitrogen gas is a colorless, tasteless, and inodorous 
body, very sparingly soluble in water, that liquid dissoly- 
ing but 13 per cent. of its volume. It is lighter than at- 
mospheric air, its specific gravity being 0-976. Its atomic 
weight is 14°19. It does not support combustion nor respi- 
ration, and from the latter circumstance obtained formerly 
the name of azote; but it does not exert any directly pois- 
onous agency on the animal system. 

Nitrogen gas is little disposed to unite with other bod- 
les, except when either it or they are in the nascent state. 
Its compounds, too, are prone to decompose from trivial 
causes; hence it is among them that we find some of the 
most remarkably detonating bodies. Many animal and 
vegetable substances, into the composition of which it 
enters, are characterized by the facility with which they 
tend to undergo putrefactive changes, and, as we shall here- 
after find, ferments owe their remarkable powers to the 
presence ‘of this element. 


Nitrogen unites with oxygen, and forms five different 
bodies, 


NG eri NORV OE EINO,.. INOS. 


How may it be made from nitrate of ammonia? What are the proper- 
ties of this gas? Why does it give rise to so many explosive bodies ? 
To what is the pie tan: of ferments due? How many compounds of oxygen 
and nitrogen are there? 


190 THE ATMOSPHERIC AIR. 


Their names are 


Protoxide of nitrogen. Nitrous acid. 
Deutoxide of nitrogen. Nitric acid. 
Hyponitrous acid. 


With oxygen, also, it forms atmospheric air; but this is a 
mixture, anal nr a compound. 


ATMOSPHERIC ATR. 


The mechanical properties and constitution of the at- 
mosphere are so important, that I shall here introduce the 
consideration of them before passing to the deme ip lies of 
the oxides of nitrogen. 

The atmosphere ¢ consists chiefly of oxygen and nitrogen 
gases, in the proportion of about 21 volumes of the former 
to 79 of the latter. It also contains a minute but essential 
quantity of carbonic acid, which, however, varies at dif- 
ferent times, 10,000 parts of air containing, on an average, 
about five parts of this gas. Besides these, there are found 
in it variable quantities of the vapor of water, and traces 
of ammonia, sulphureted hydrogen, and carbureted hy- 
drogen. It is a colorless, invisible, elastic substance, 815 
times lighter than water, and is taken as the standard of 
comparison for the specific gravity of gases. Its specific 
gravity is, therefore, = 1:000. One hundred cubic inch- 
es of it weigh, at the mean temperature, and pressure very 
nearly 31 grains. 

There are many methods by which the analysis of the 

Fig. 177. air can be effected. Ure’s eudiom- 
eter, Fig. 177, which consists of a 
siphon tube, closed at one end and 
open at the other, may be used for 
this purpose. Into the closed branch 
of the instrument, which is also grad- 
uated, a measured quantity of air is 
introduced, and to it is added an 
equal volume of hydrogen. The 
bend of the tube is occupied by wa- 
ter, as shown in the figure, a column 
of air intervening between this water and the open ex- 
tremity of the tube. Oni this the thumb is closely pressed, 


. 


Of what is the atmospheric air composed? What is its specific grav- 
ity? What is the weight of 100 cubic inches of it? How may it be an- 
alyzed by Ure’s eudiometer? 


ANALYSIS OF THE AIR. 191 


as represented, and an electric spark passed through the 
instrument by the aid of its platina wires. This sets the 
gases on fire; the column of air beneath the thumb acting 
like a spring to repress the movement at the time of the 
explosion. The amount of gas then left is ascertained on 
the divisions, and one third of the deficit represents the 
quantity of oxygen originally present. 

To enable the experimenter to operate on larger quan- 
tities of gas, Brunner’s instrument may 
beused. It consists of a tube, a de, with 
three bulbs blown upon it; these bulbs 
are filled with cotton which has been im- 
pregnated with melted phosphorus. The 
tube is attached, by means of a cork, to 
a glass vessel, d, filled with mercury. On 
opening the stop-cock, e, the mercury 
flows out, atmospheric air introducing 
itself by a b c, and its oxygen being re- 
moved by means of the extensive surface 
of phosphorus which the cotton presents. 
Consequently, by measuring the mercury 
which has flowed out we ascertain the 
quantity of nitrogen introduced into the vessel d, and the 
increased weight of the tube a & c determines the amount 
of oxygen. 

The result of such experiments shows that the atmos- 
pheric air is composed of from 20°79 to 21:08 parts of 
oxygen in 100 volumes. By weight, its constitution is 
about, | 


CEyeee wt ee Oe 
Nitrogen . . . . 76°96 
100°00 


The earth’s atmosphere does not extend indefinitely 
into space, but termmates at an altitude of about fifty 
miles. It forms, therefore, a mere film on the face of 
the earth, for the diameter of the globe is nearly 8000 
miles. Ifarepfesentation of it were placed on a common 
twelve-inch globe, it would scarcely be one eighth of an 
inch thick. | 

Its relations to the world of organization are full of in- 
terest. All plants come from it and all animals return to 


How by Brunner’s instrument? What is its constitution by volume and 
by weight? To what distance does it extend? 


192 DENSITY OF THE AIR. 


it, so that it stands as the bond of connection between 
these orders of life. 

As we ascend to more elevated regions the air becomes 
less dense, for the obvious reason that, as it is a very com- 
pressible body, those portions of it nearest the ground 
have to sustain the weight of the superincumbent mass, 
and are therefore more dense; but in the higher regions, 
where the superincumbent pressure is less, the air is more 
rare, as is shown in the following table: 


Height in Miles. | Volume of Air.| Barometric Inches. 


which also shows that the great mass of the atmosphere is 

comprehended within a very short distance of the earth’s 

surface. At different altitudes it is of very different tem- 
eratures, being colder as the altitude is greater. 

Of the constituents of the air, the oxygen and nitrogen 
are usually spoken of as fixed, the carbonic acid, ammo- 
- nia, and water as variable. Tiere are causes in operation 
which tend continually to impress changes in the amount 
of all these bodies. Every process of combustion, and the 
respiration of every animal, remove oxygen and replace 
it by carbonic acid. But the growth of plants has the re- 
verse action, removing carbonic acid and replacing it by 
oxygen, so that for many centuries in succession the con- 
stitution of the atmosphere is unchanged. 

Of the mechanical properties of the air, the first to 
Fig. 119. which we have to direct our attention is its press- 
ure, which takes effect equally in all directions, up- 
ward, downward, and laterally. Thus, if we take 
a glass tube several feet long, a, Fig. 179, closed 
at one end and open at the other, and having filled 
it full of water, place over the auth of it a piece 
of card, b, and turn it upside down, the card will 
not fall off, nor the water flow out; they remain, 
as it were, suspended on nothing, but in reality sus- 


What are its relations to animals and plants? Why does its density 
decrease with the altitude? How does its temperature vary? Which 
are the fixed, and which the variable constituents of the air? Give some 
illustrations of the upward pressure of the air. 


PRESSURE OF THE AIR. 193 


tained by the upward pressure of the air. Or if we take 
a bottle, a, fg. 180, with a hole, 6, half an inch Fig. 180. 

in Bianieter 4 in the Beran of it, and having filled e 

it with water, close the mouth ‘oft it with the fin- 

ger, it may be held up in the air without the wa- 
ter flowing out, although the aperture 4 is wide 
open. In this instance, again, it is the upward 

pressure of the air which sustains the liquid. i} 

Let the glass globe a, Fig. 181, with its neck ye. 181, 
5, be iivestadls in some water enataiaks in ajar, 
c, and the whole covered by an air-pump re- 
ceiver. As the receiver is exhausted, bubbles 
of air pass through the water and escape away, 
but as soon as the pressure is restored the 
water is forced out of the jar upward into the 
globe. 

The air-pump enables us to exhibit in a very striking 
manner many of the chief mechanical properties of the at- 
mosphere. ‘Thus, if upon the plate of it there 
be placed a glass receiver, a, Hg. 182, as soon 
as the air is exhausted from its interior, the su- 

erincumbent pressure retains the glass so firm- 
ly in contact that it is impossible to lift it off, 
Fig. 184. but as soon as the air is readmit- 

é ted it can be easily removed. If 
within the receiver a@ a smaller one, 6, be 
placed, and exhaustion made, while a is fixed 
6 can be easily moved by shaking the pump, 
but on letting in the air, a becomes loose and 
é firmly pressed in contact with the plate. 

If over the mouth of a _ Fig. 183. 

-jar, ’g.183, placed upon 
the pump, the palm of 
the hand be laid, as the © 
air is exhausted it is 
pressed in close contact 
with the jar, and can only 
be removed by the exertion of a very con- 
siderable force. 

On a small plate, a, Hig. 184, furnish- 

ed with a stop-cock, 4, terminating in a fine 


Give an illustration of its downward pressure, Describe the experi- 
ment represented in ig. 183. 
R 


194 PRESSURE OF THE AIR. 


jet, ¢, let there be placed a tall glass receiver. The stop- 
cock being now screwed into the pump and opened, the 
air may be exhausted from the interior of the receiver 
and the stop-cock closed. But being now opened under 
the surface of some water in a cup, the water passes 
‘through the jet and rises to the top of the jar, forming a 
fountain in vacuo. 


LECTURE XLIII. 


Armospuertc Air.— Pressure of the Air.—Simple Means 
of Exhaustion.— Determination of the Weight of Air.— 
Amount of Pressure—— Elasticity of Air—Ezists in the 
Pores of Bodies—Respiration of Fishes.—Measure of 
Elastic Force. 


Tue Magdeburg hemispheres, mvented by Otto 
Guerick, who also invented the air pump, illustrate in a 
very striking manner atmospheric pressure. They con- 

Fig. 185. sist of a pair of brass hemispheres, a b, Fig. 
185, with handles ; they fit, without leakage, to 
each other by a flange, so as to form a perfect 
sphere. One of ane eae a stop-cock, through 
which the air may be exhausted, aad on this 
being. done, it will be found Sect impossible 
to pull them apart, though as soon as the air is 
readmitted, and its pressure restored to the in- 
terior, they will fall asunder by their own weight. 

If over the mouth of an open receiver, a, Fig. 186, a 

Fig. 186. piece of bladder be tightly tied with a waxed 
Ssa;, thread, when the air is exhausted the bladder 
becomes deeply depressed into a spherical con- 
cavity by the superincumbent pressure, and 
finally bursts inward with a loud explosion. 

€ Itis upon the principle of atmospheric press- 
ure that the various instruments used by surgeons for cup- 
ping act. One of the most simple methods of performing 
this operation is ‘to place the cupping glass for a moment 
over the flame of a spirit lamp, and then transfer it rapid- 


Describe the fountain in vacuo. Whatare the Magdeburg hemispheres ? 
What is the principle illustrated in these various experiments ? How 
is the process of cupping performed ? 


WEIGHT OF AIR. 195 


ly to the skin. Spirits of wine, when burning, forms a 
very large quantity of steam, which, of course, fills the in- 
terior of the glass in a rarefied state by reason of the high 
temperature of the flame. As soon as this steam con- 
denses a vacuum is formed, and the soft surface on which 
the cup is placed is pressed into its interior. 

For many of these experiments, an air pump is not nec- 
essarily required, but simple contrivances will answer in 
its stead. Thus, if we take an eight-ounce __ Fig. 187. 
vial, a, Fig. 187, and fit to the mouth of it 
a cork, b, through which there passes a piece 
of glass tube, ¢, drawn into a narrow jet at 
one extremity, but open at the other, by pla- 
cing the finger over the opening and intro- 
ducing it into the mouth, the air, by the ac- 
tion of the tongue and the muscles of the mouth, may be 
sucked out to a great extent; and when the exhaustion 
has been carried, by this means, as far as possible, by 
pressing the finger over the opening, it will close it, act- 
ing, therefore, asavalve. And now, if the bottle be turned 
upside down, as at e, the tube dipping beneath some wa- 
ter in a cup, as soon as the fin- Fig. 188. 
ger is removed the water is press- . 
ed upward, and forms a fountain 
in vacuo. 

- The pressure of the air depends 
primarily on the fact that it is a 
heavy body, as may be proved by 
the direct experiment of weighing 
it. For this purpose, let a light 
glass flask, a, Pig.188, fitted with 
a stop-cock, be counterpoised at 
the balance; then let the air be 
exhausted from it, and its weight 
determined again. It will now 
be found lighter than before; but 
upon opening the stop-cock it 
will regain its original weight. 
Experiments made in this man- 
ner show that a flask contain- 
ing 100 cubic inches will, when 


Describe a simple method by which partial exhaustion may be pro- 
duced by the mouth. How may the weight of air be directly ascertained ? 


196 SPECIFIC GRAVITY OF GASES. 


exhausted, weigh about thirty-one grains less, and there- 
fore we infer that that is the weight of 100 cubic inches 
of atmospheric air. 

Atmospheric air is used as the standard of comparison of 
the specific gravities of other gaseous bodies. The process 
for the determination is very simple. A glass globe, g, 

Fig. 189. Fig.189, holding 20 or 30 cu- 
“\. bic inches, is exhausted of air, 
and by means of the stop- 
cocks, e d, attached to the jar, 
c, containing the gas to be 
tried. This gas, which is con- 
fined by mercury, has been 
passed through the drying 
tube, a, by the delivering 
H\ tube, b, into the jar, which 
= ==] should be graduated. On 
mi] Opening the cocks, e d, the 
“gas flows into the exhausted 
globe; the quantity introduced may be determined on the 
graduation, and its weight ascertained by the balance. 

There are several different methods of stating the 
amount of the mean pressure of the air; thus, we say that 
it is equal to 15 pounds on the square inch, or to a col- 
umn of mercury 30 inches long, or to a column of water 
30 feet long. 

That air is a highly elastic substance, can be readily 
shown. Under a receiver (Ig. 190) let there 
be placed a half-blown bladder, the neck of 
which is tightly tied ; as the air is removed from 
the receiver the bladder distends, 
but, on restoring ‘the pressure, it 
| becomes as flaccid as it was be- /, 
| fore, showing that the air included [ 
in it expands and contracts as the ||: 
pressure upon it is made to vary. ; 

This may be still better shown by taking 
a small India-rubber bag (fg. 191), the 
mouth of which is closed tightly, and using 


Z 


Fig. 190. 


In what manner may the relative weight of other gases be determined ? 
What is the pressure of the airona square inch equalto? What is nearly 
the equivalent length of a mercurial and water column? How may the 
elasticity of air be illustrated ? 


ELASTICITY OF AIR. 197 


it instead of the bladder in the last experiment. On rare- 
fying the air in the receiver, the bag begins to dilate, and 
may be extended to several times its original dimensions, 
as shown in the dotted line; but as soon as the pressure 
is restored, it returns to its original size. 

Nor does this expansion take place with an yg, 199, 
inconsiderable force. Ifa flaccid bladder be 
placed, as in Fig. 192, with several heavy lead- 
en weights put upon it, as soon as it is caus- 
ed to dilate by removing the pressure, it will 
push up the weights. Nor does it lose its 
elastic force or spring by being long pent 
up in close vessels. Some of the old chem- 
ists kept air compressed in copper globes for 
months, and found that, as soon as an opening was made 
for it, it expanded to its original dimensions. 

Let there be taken a glass bulb, a (fug. 193), the open 

neck of which, 4, dips beneath some water in Fig. 193. 
a jar, e, and let the bulb and tube be full of 
water, with the exception of a small space oc- 
cupied by atmospheric air. On covering the 
apparatus with an air-pump receiver, d, and 
exhausting, the bubble of air, a, gradually ex- 
pands, and after a time, as the action of the 
machine is continued, fills the entire glass, both 
bulb and tube; but as the pressure is restored, it con- 
tracts again, and goes back to its original size. 

By taking advantage of the expansibility of air under 
Fig. 194. reduction of pressure, we are able to dem- pig. 195, 
onstrate its existence in the pores of many 
), bodies; thus, if we place in glasses of. 
| water an egg (Fug. 194), an apple (Fug. | 
| 195), or other such objects, and, covering 
them with a receiver, exhaust, we shall 
see innumerable bubbles of air escaping 
through the water. The same observa- 
tion may be made in the case of many ¢ 
— liquids which hold gaseous substances dis- © 
solved. A glass of ale placed in an exhausted receiver 


How may the elasticity of air be shown by an India-rubber bag? Give 
an illustration of the amount of this force. How may the presence of air 
be detected in the pores of solid bodies? How may air be shown to exist 
dissolved in liquids ? 

R 2 


198 RESPIRATION OF FISHES. 


Fig.196. (Fig. 196) foams from the escape of carbonic 

c acid gas, and even clear spring or river water, 
examined in the same manner(Jvg. Fig. 197. 
197), is found to contain a large C 
quantity of air in solution. 

This last fact is of considerable 
importance, for it is by the aid of 
this air that the respiratory function 
of fishes is carried forward. On ff) 
examination, however, it is found that this is @e@l 
not true atmospheric air, 
but a mixture, which is eieod in oxy- 
gen. ‘The atmosphere contains 21 per 
cent. of oxygen, but this gas contains 
33. The cause of the difference is the 
unequal solubility of oxygen and nitro- 
gen; for the former gas, being much 
the more soluble, the water takes up 
relatively a greater portion of it from 
the air. Fishes, therefore, respire this 
gas, its richness In oxygen making 
up for its inferior amount; and when 
they are placed in water which has 
been in an exhausted receiver, they die. Their move- 
ments, also, are, to a certain extent, regulated by the air 
contained in a receptacle, or bladder, in their bodies; by 
the compression of it they can descend, and by its expan- 
sion rise. If they be placed in water in a partially ex- 
hausted receiver, they float on the surface, or can only 
descend to the bottom for a moment by violent muscular 
exertion. 

Fig. 199. The necessity of air to the support of com- 
bustion may be illustrated by comparing the 
length of time a candle will burn in a large 
receiver full of air, and in the same exhaust- 
ed, Fig. 199. In the latter case it speedily 
dies out, the smoke descending to the bottom 
of the jar in the rarefied medium around. 

Substances prone to decay, such as meats 
and fruits, may be preserved for a length of 
time in vessels void of air. The process is 


Of what use is the air dissolved in water? What is its composition? 
How may the necessity of air to the support of combustion be proved ? 


Y= 


+ 
PRESERVATION OF FRUITS. 199 


illustrated in Fig. 200. The Fig. 200. 
fruits are placed in a large jar tif 
closed by a sound cork, covered 
with sealing-wax. A small hole 
is made through the cork, and 
the ] jar cover ed by an air-pump 
receiver. On exhausting, the 
air passes out through the hole, 
and when the vacuum is per- 
fect the hole is closed by melt- 
ing the wax by the sunbeams 
converged by a convex lens, 
the access of the air being thus 
cut off. 

From ‘the foregoing experiments and considerations, it 
appears that the primary fact in pneumatics is, that the 
air has weight; from this, by a necessary consequence, 
arises its pressure and the inequality of density of the at- 
mosphere at different altitudes. It also follows that the 
elastic force of the air must be precisely equal to the 
pressure upon it. In any given stratum of air, as, for in- 
stance, that which rests upon the surface of the earth, the 
pressure of the superincumbent mass is equipoised by the 

~elastic force ; if the elastic force were less, compression 
would ensue; if greater, dilatation. The pressure and the 
elastic force mitist: therefore, be equal to each other. 


LECTURE XLIV. 


Atmospueric Air.— The Barometer.— Description of tt.— 
Cause of the Phenomenon.—Proof that it is the Pressure 
of the Air—HListory of the Invention.—Paschal’s Ex- 
periment.—LIllustrations of the Nature of Pressure— 
Variability of Pressure—Point of Perpetual Congela- 
tion.— Local Disturbances in the Constitution of the Air. 
—Diffusion of Gases —The Air is a Mixture—Mar- 
riotte’s Law—Gay-Lussac’s and Rudberg’s Law. 


Ir we take a tube of glass, a 3, fig. 201, page 200, more 
By what means may objects be preserved from its influence? What 
is the relation between the pressure and the elastic force of the air? 


5 * 


200 THE BAROMETER. 


Fig. 201. than thirty inches long, closed at one end and open 
at the other end, and, having filled it with quick- 
silver, invert it in a cup, ¢c, filled with that metal, the 
mercury will not flow out of the tube, but will 
remain suspended at a height of twenty-eight or 
thirty inches. If there be placed beside Fig. 202 
the tube ascale, d, divided into inches and ‘3 
decimal parts, the zero of the division 
coinciding with the level of the mercury 
in the cup, stich an instrument forms the 
wm © barometer. 

The cause of the suspension of the mercury in 

the tube is the pressure of the air. This may be 
demonstrated by placing over the barometer a 
tall air-pump receiver, and exhausting. It will 
be found that, as the pressure in the interior of 
the receiver is reduced, the column of mercury 
in the barometer falls, and on restoring the press- 
ure it rises to its original point. 
Fig..03. Lhe same fact may be proved in another manner 
If a tube, upward of thirty inches long, the upper 
extremity of which is closed by a piece of bladder, 
be filled with mercury and inverted in a cup, as 
shown in J”g. 203, the bladder will be found deep- 
ly depressed, the pressure of the air in that di- 
rection being borne by it; but if now a minute pin- 
hole is made in the bladder, so as to allow the air 
to press upon the top of the mercury, the column 
s” rapidly descends, flowing out of the tube. 

The barometer was originally invented by Torricelli. 
Some plumbers, working for the Duke of Florence, found 
that it was impossible to make a pump which should raise 
water more than about thirty feet. This fact eventually com- 
ing to the knowledge of Torricelli, he suspected that the 
water rose in those machines in consequence of the pressure 
of the air, and not through Nature’s abhorrence of a vac- 
uum, as was at that time supposed. But if the limit to 
which water can be raised by a pump is reached when the 
pressure of the column of liquid equilibrates the pressure 
of the air, it follows that if a heavier fluid than water be 


Describe the barometer, What is it which supports the mercurial col- 
umn? How may this be proved? By whom was the barometer invent- 
ed? What were the circumstances of the invention ? 


@y 


PRINCIPLE OF THE BAROMETER. 201 


used, the height to which it can be raised is less. A pump 
ought, therefore, to lift quicksilver only about as many 
inches as it can lift water feet; for the weight of these 
liquids is about as one to thirteen and a half, and, accord- 
ingly, Torricelli found, by means of a small pump fixed. 
to a long glass tube, that such, in reality, is the case. The 
barometer is a simplification of the same apparatus. 

That it is the pressure of the air which sustains the mer- 
curial column was satisfactorily proved by Paschal, who 
reasoned that, if this were the case, the barometric column 
ought to be shorter on the top of a mountain than in a 
valley, because in the former position that pressure must 
necessarily be less. On the experiment being made, his 
reasoning was found to be true. 

The principle of the barometer may be illustrated by 
substituting for the pressure of air the pressure of a col- 
umn of water. Thus, if we pour some quicksilver into 
the bottom of a deep glass jar, a, Fug. 204, and Fig. 204. 
plunge into it a long tube, 4, open at both ends, 
the quicksilver will rise in this tube, so that its 
level on the inside will be coincident with that on 
the outside. But if now we begin to fill the jar 
with water, c, for every thirteen and a half inches 
in depth poured in, the quicksilver, d, will rise 
one inch, the mercurial column counterpoising 
the column of water. And, on the same princi- @ 
ple, the column of quicksilver in the barometer counter- 
poises that of the air to the top of the atmosphere. 

Mr. Boyle discovered that the pressure of the air is not 
always the same, but it undergoes many variations, the 
mercurial column sometimes falling near to 27 inches, or 
rising above 30. The range is commonly estimated at 
25 inches. It is considerably less in the tropics. These 
changes of pressure are exceedingly irregular, and are 
connected with meteorological phenomena. There are 
also diurnal variations, the column rising twice in the 
twenty-four hours. In winter the first maximum is about 
nine A.M., and the minimum at three P.M., the second 
maximum being about nine P.M. 


What was Paschal’s experiment? What did it prove? How may the 
phenomena of the barometer be illustrated by the pressure of a water 
column? What is the extent of the irregular variations of pressure? What 
are ne diurnal variations? At what times do the maxima and minima 
occur 4 


202 DIFFUSION OF GASES. 


It has already been observed that the mean pressure of 
the air is estimated at 15 pounds upon a square inch, or 
equal to a column 30 inches long. A man of average size 
sustains a pressure on the surface of his body of nearly 
thirty thousand pounds. 

The temperature of the atmosphere is lower as we as- 
cend to more elevated regions. A point, therefore, can 
always be reached over any place of which the tempera- 
ture never rises over 32° I’., and where water is always 
frozen. This point is known under the name of the point 
of perpetual congelation. Its altitude differs very much 
in different places, being highest at the equator, and low- 
er as we go toward the poles. It is at 


The Equator. . . . 15,000 feet. 
Letitaude: 40°. estes a & BOO £5 
Coed ao ee RL tae 
of ce ne es ihre 


Many causes conspire to give rise to local disturbances 
in the constitution of the air. In its lower strata combus- 
tion and respiration are actively going on; they tend to 
diminish the oxygen and increase the Zonnite acid. At 
the equator the effect of a constantly brilliant sunshine on 
the leaves of plants is to diminish the carbonic acid and 
increase the oxygen. But notwithstanding these local dis- 
turbances, and also the fact that the constituents of the 
air are of very different specific gravities, the constitution 
of the atmosphere is nearly the same in all places. This 

Fig. 205. commixture is partly effected by the mechanical 
action of winds, and partly by the property which 
gases have of diffusing into each other. Thus, 
if two vials, a and e, Fie. 205, communicate ood 
each other by means of stop- -cocks, bcd, and if, 
in a, a light gas, such as hydrogen, is placed, and 
inéa heavy : gas, as carbonic acid, in a few min- 
utes after the stop-cocks are opened the gases 
will diffuse into each other, the light one descend- 
ing and the heavy one ascending, until they are 
perfectly commixed. And this effect will take 
place even though a barrier should intervene. 
| Thus, Dr. Mitchell found that gases would read- 
ily pass through the close texture of India-rub- 


ap 


See 


aGns 
Ss 
ae 
a SES 


What is the point of perpetuai congelation? How does it vary with 
the latitude? What are the causes which tend to change the composi- 
tion of the air? What is meant by the diffusion of gases ? 


MARRIOTTE’S LAW. 903 


ber to mingle with each other; and I have observed the 
same in the case of films of water. Thus, if a Fig. 206 
bottle, a, Fig. 206, full of atmospheric air, have its “e — 
mouth closed by a film of soap-water spread over 
it by the finger, and then be placed under a bell 
jar containing protoxide of nitrogen, this latter 
gas passes rapidly through the film, and distends § { 
it into a bubble by forcing its way into the bottle. “= 
The force with which gases will thus pass into each other 
is sometimes very great. Ihave proved that sulphureted 
hydrogen will diffuse into atmospheric air, though resist- 
ed by a pressure of more than fifty atmospheres. 

That the atmospheric air is a mixture, and not a com- 
pound, is proved by its easy decomposibility, its refract- 
ive power, and by the fact that its constituents retain their 
properties unchanged. ‘The amount of its oxygen may be 
determined by the combustion of phosphorus, or detona- 
tion with hydrogen ; the amount of its carbonic acid, which 
varies in. damp or dry seasons, being dissolved out by 
showers of rain, may be determined by potash or lime- 
water, and its aqueous vapor by the process for the dew- 
point already described. 

Atmospheric air being thus an elastic and compressi- 
ble body, it remains to explain the law which de- Fig. 207. 
termines its volume under changes of pressure. | 
‘This is known under the name of the law of Mar- 
riotte, and, applying to many other gases besides 
atmospheric air, is to the effect that the volume of | 
a gas is inversely as the pressure upon it. ‘This law 
is of the utmost importance in gaseous chemistry. | 
It may be illustrated by the instrument (/%g. 207), 
where a bd is a bent tube, open at the end a, and 
closed at 6. The branch a may be several feet 
long, and @ six inches. A small quantity of mercury is 
poured into the tube, so as to occupy the bend and shut 
up a column of air between d and 6. Now, if the tube is 
filled with quicksilver to the height of 30 inches, as to a, 
the pressure of this column is exerted on the air in the 
closed branch, 4 ; and as there are now the weight of two 
atmospheres, that of the ordinary atmosphere and that of 


Does this take place through intervening barriers? How is this con- 
nected with the constitution of the air? What proofs are there that the 
atmosphere is a mixture, and not acompound? What is Marriotte’s law ? 
How may its truth be proved? Give examples of Marrictte’s law. 


204 DILATATION OF ATMOSPHERIC AIR. 


the mercurial column, it is compressed into half its former 
volume, c. If we bring upon it three atmospheres, it will 
be compressed into one third; if four, to one fourth, &c. 
And the law holds good, also, for diminutions of pressure. 
If, on a given volume of gas, the pressure is reduced to 
one half, the volume doubles ; if to one third, it triples ; 
to one fourth, it quadruples ; in all cases the volume being 
inversely as the pressure. 

The exact amount of dilatation of atmospheric air for 
elevations of temperature was determined by Gay-Lussac 
as follows: In a tin box, A, containing water, there is in- 


on Fig. 208. 


ae a ee 


geaoe ona, 
ie 


we aj 


troduced through a perforation at o! a bulb, g, with a tube, 
g', containing the air, the dilatation of which is to be 
measured. ‘This air has been previously introduced in a 


TI i 


in 


i 
£865, or: O72 
Wire Oa) 


state of dryness by the chloride of calcium tube, 2h’. At_ 


m is a globule of mercury, which acts as an index, and 
confines the air. On the opposite side of the tin box, at 
o, a thermometer, s ¢ b, is mtroduced, and another one, v, 
passing through the top of the box, occupies the center. 
The box is first filled with water containing fragments of 
ice, and when the thermometers are at 329, the position 
of the index, m,is marked. The furnace is then lighted, 
and when the water boils, and the thermometers are at 
212°, the index, m, is again observed. The difference 
indicates the dilatation of the air for 180°; and in this 
manner Gay-Lussac found that 1000 volumes of air be- 
come 1375. These results have been of late carefully ex- 
amined by Rudberg, who fixes the amount of expansion 
of air at ;4, of its volume, at 32°, for every degree of 
Fahrenheit’s scale. 


What is the law of Gay-Lussac? Whatis the absolute dilatation of air 
‘as determined by Rudberg? 


PROTOXIDE OF NITROGEN. 205. 


LECTURE XLV. 


Compounps or NirroGEN AND OxyeGEen.—Protoxide of 
Nitrogen.—Preparation and Properties of—Constitu- 
tion.— Supports Combustion.— Produces Intoxication. 

Deutoxide of Nitrogen.—-Preparation and Properties of. 
— Constitution.— Relations to free Oxygen.— Hyponitric 
Acid.— Preparation and Properties of. 


PROTOXIDE OF NITROGEN. NO = 22:203 
Ir the nitrate of ammonia be exposed to a temperature 

of about 350 degrees in a retort, Fig. 209. 
Fig. 209, it undergoes decompo- 
sition, being resolved into water 
and the protoxide of nitrogen ; the 
former condensing in the neck of 
the retort, and the latter rising 
into the pneumatic jar. If whitish CZ’ © _ 
fumes are evolved, they indicate that the process is going 
on too fast, and the heat must then be moderated. The 
change taking place is very simple. It is a mere rearrange- 
ment of the constituent atoms of the nitrate of ammonia. 


NO, + NH,... = ...2(NO) + 3(HO). 


One atom of that salt, therefore, yields two atoms of 
protoxide of nitrogen and three of water. 

The protoxide of nitrogen is a colorless gas, transpa- 
rent, like atmospheric air; it has a sweetish taste, and is 
soluble in water, that liquid taking up about three fourths 
of its volume of the gas when cold, but the solvent power 
being greatly diminished by warming the water. Its 
specific gravity is 1527. It may be liquefied at rig. 210. 
45° by a pressure of fifty atmospheres, and has 
even been solidified. It is composed, by atom, of 
one of nitrogen and one of oxygen, and by vol- , 
ume, of two volumes of nitrogen united to one of / 
oxygen, condensed into two volumes, a constitution { 
like that of water. It therefore contains half its \ 
bulk of oxygen gas, and supports combustion with 


How may protoxide of nitrogen be made? What are its properties ? 
What is its constitution? Does it ee combustion ? 


206 DEUTOXIDE OF NITROGEN. 


activity. A lighted taper immersed in it burns brightly, 
and, as in oxygen, if there be merely a spark on the wick, 
it kindles into aflame. Phosphorus burns in it with great 
brilliancy. 

Sir H. Davy discovered that not only does this gas sup- 
port respiration, but that it exerts a remarkable physio- 
logical action when breathed, producing a transient in- 
toxication, which wears off after two or three minutes. 
These effects are undoubtedly due to the oxydizing ac- 
tion which the protoxide establishes in the system. In 
this respect it is far more active than even pure oxygen 
gas, and the reason is obvious: oxygen is but slightly ab- 
sorbable by watery fluids, but this gas is taken up by 
them to a very great extent. When it is introduced into 
the lungs, it is rapidly dissolved in the blood, and carried 
by the circulation to every part of the body, oxydizing 
whatever is in its path, and producing a febrile warmth 
and an unusual mental disturbance. 

The protoxide of nitrogen shows but little disposition to 
unite with other bodies. It may be regarded as an in- 
different substance. 


DEUTOXIDE OF NITROGEN. NO, = 30°216. 


The deutoxide or binoxide of nitrogen may be made 
by the action of nitric acid moderately diluted upon me- 
tallic copper. If these substances are introduced into a 

Fig.2i1. flask together, and, when the action mod- 
erates, fre esh portions of nitric acid be added 
through the funnel (J/g. 211), a colorless gas 
is evolved, which may be collected over wa- 
ter, in which it is only sparingly soluble, one 
hundred volumes of that liquid dissolving 
about five of the gas. 

——— Itis composed of equal volumes of nitrogen 
and loxygen united, without condensation. Its specific gray- 
ity 1s, therefore, 1-0416. It does not support combustion ; 
a lighted taper immersed in it is at once extinguished ; 
but if phosphorus, burning violently, be introduced in it, 
the combustion goes on with increased activity. Iron 
and several other metals withdraw from ‘it one half of 
its oxygen, converting it into the protoxide. 


‘What are its relations to respiration? How long does this intoxicating 
effect last? What is the cause of it? Why is the protoxide of nitrogen 
an indifferent substance ? How is the deutoxide obtained? What is its 
constitution? Does it support combustion ? 


HYPONITROUS ACID. 207 


The most remarkable quality of the deutoxide of nitro- 
gen is its action on mixtures containing oxygen gas, as, 
for example, atmospheric air; with these it at once pro- 
duces red fumes of nitrous eer which are soon removed 
if water be present, the deutoxide taking up two atoms 
of oxygen to change into nitrous acid. On this principle 
it has been used for the purpose of effecting the analysis 
of atmospheric air, but, unless several precautions are ob- 
served, the results are incorrect. The deutoxide should 
be added in a small and steady stream to the air; red 
fumes are at once produced; these are soon removed by 
the water, and the residue is less in volume than the air 
and deutoxide taken together. One fourth of the deficit 
is equal to the volume of the oxygen originally present. 
By operating in this manner, as I have had many occa- 
sions to observe, correct results may be obtained. The 
general process may be illustrated by taking a tall jar 
and placing in it a certain volume of atmospheric air, to 
which is to be added an equal volume of the deutoxide. 
Though both gases are colorless at first, a deep copper- 
colored vapor is the result; this is removed after a time 
by the action of the water, which, rising in the jar, ex- 
hibits a deficit in the amount of the gases. 

A solution of the protosulphate of iron dissolves this 
gas abundantly; and if a small quantity of the sulphuret 
of carbon be poured into it, and a light applied, the mix 
ture burns with a blue aie: 


HYPONITROUS ACID. NO, = 38°229. 

This substance may be made by mixing four volumes of 
dry deutoxide of nitrogen with one of ‘dry oxygen, and 
exposing the mixture to cold. The gases condense into 
a liquid of a greenish color, which gives forth an orange 
vapor. Hyponitrous acid is decomposed by the contact 
of water, deutoxide of nitrogen escaping with an effer- 
vescence, and nitric acid being produced, three atoms of 
hyponitrous acid yielding one of nitric acid and two of 
the deutoxide. 

DINOS es =. oe NOSE 2I1V03. 

What is its action on gaseous mixtures containing oxygen? Under 
what circumstances may it be used to determine the amount of oxygen? 
How may its action on oxygen mixtures be illustrated? What is its re- 
lation with the protosulphate of iron? And what with the vapor of sul- 


phuret of carbon? How may hyponitrous acid be procured? What is 
the action of water on it? 


208 NITROUS ACID. 


LECTURE XLVI. 


Compounps or Nitrogen anp Oxyeren.—WMitrous Acid. 
—Preparation and Properties of —Remarkable Changes 
of Color.— Nitric Acid.— Discovery of— Cavendish’s 
Experiments.— Sources from which rt is Derived.— Com- 
mercial Preparation —lIts Properties.—Is a Hypothet- 
ical Body.—Purification.— Detection. 

NITROUS ACID. NO, = 46-242. 

Nrrrovus acid may be made by mixing together one 
volume of dry oxygen with two of the dry deutoxide of 
nitrogen, and exposing the mixture to a very low tem- 
perature ; but it is much more easily procured by distill- 
ing, in a porcelain or hard glass Fig. 212. 
retort, a, Fig. 212, dry nitrate of i! 
lead, and receiving the gases in 
a tube, 4, artificially cooled by a 
freezing mixture, c. The nitrous ¢% 
acid condenses as a colorless liquid, . 
which becomes yellow as its temperature rises. Its spe- 
cific gravity, in the liquid form, is 1°42. It solidifies at 
40° I., and boils at 82° I’. Its vapor possesses remark- 
able optical qualities. When its temperature is very low, 
it is nearly colorless; it takes on an orange tint as the 
degree of heat increases, and finally becomes almost 
black. The peculiarity of the phenomenon is, that if the 
gas be examined while undergoing these changes, by 
passing a ray of light through it and analyzing it by means 
of a prism, as explained i in Lecture XIX., a great number 
of fixed lines are found in the resulting spectrum ; and as 
the temperature rises these increase so much in number 
and in breadth that the light becomes finally obliterated. 

The vapor of nitrous acid, when once mixed with atmos- 
pheric air, is condensed into the liquid form with great 
difficulty. It is wholly irrespirable, and, even when di- 
luted, of a very unpleasant odor. Nitrous acid is, for the 
most part, alan cf water, 

3NO,. .. 2INO; + NO,, 
~ How may nitrous al. be made? What are its properties? How does 


the color of its vapor change by heat? What is the cause of the final 
blackness? What are the ‘relations of nitrous acid and water? 


% 


NITRIC ACID. 209 


three atoms of it yielding to two of nitric acid and one of 
the deutoxide of nitrogen, as seen in the formula; but 
the nitric acid produced protects a portion of the nitrous 
acid, which thus escapes decomposition. Its vapor is ab- 
sorbed by nitric acid. The production of this acid by the 
process with nitrate of lead is of considerable philosoph- 
ical interest ; 
PbO + NO;...=...PbO0-+ NO,+ O, 

one atom of the nitrate of lead yielding one atom of ox- 
ide of lead, which remains in the retort, one of nitrous 
acid, and one of oxygen gas, which escape. - It might be 
expected that, in such a distillation, we should obtain 
oxide of lead and nitric acid. ‘The cause of the non-ap- 
pearance of the latter body will, however, be presently 
understood. 


NITRIC ACID. NOs = 54:255. 


Nitric acid, the most important of the compounds of 
oxygen and nitrogen, and one of the most.important of 
the acid bodies, was first discovered during the ninth 
century. The discovery of this and some of the other 
powerful acids form one of the epochs in chemistry. The 
science can scarcely be said to have existed until that 
time, the Egyptians, Greeks, and Romans having no 
knowledge of these bodies, nor, indeed, of any more pow- 
erful than vinegar. 

The constitution of nitric acid was determined by Mr. 
Cavendish, who formed it synthetically, by passing electric 
sparks through atmospheric air in contact with a solution 
of potash. ‘The nitrate of potash was obtained. 

Nitric acid also occurs to a small extent in rain water, 
especially after thunder storms, and by some supposed to 
originate upon the same principles as in Cavendish’s ex- 
periments ; but probably it is due to the oxydation of 
ammonia, which always exists in the air. The chief sup- 
ply is derived indirectly from the decay of vegetable or 
animal matter, in the presence of oxygen gas, and in con- 
tact with basic bodies. Collections of such refuse pass 
under the name of nitre beds, and, in France and Ger- 


What is the decomposition which takes place when nitrate of lead is 
distilled? When was nitric acid discovered? How was its composition 
determined by Cavendish? What is the source of the nitric acid in rain 
water! 

S 2 


é... 


210 NITRIC ACID. 


many, furnish the saltpetre which is used for the manu- 
facture of gunpowder. In the East Indies, nitrate of 
potash is obtained by lixiviation from the soil in which 
earthy nitrates naturally occur. From South America 
the nitrate of soda is exported; it is found as an efflo- 
rescence on soils in which common salt probably exists. 

In most of these cases the nitric acid arises from the 
oxydation of ammonia produced during putrefactive fer- 
mentation. 


NEL, fun Seok FIV Osteo 0. 


The formula shows the probable nature of the action; one 
atom of ammonia, under the influence of eight of oxygen, 
will yield one of nitric acid and three of water. 

The nitric acid of commerce is made by distilling equal 
weights of sulphuric acid and nitrate of potash. The 
process may be conducted in a small way in a glass re- 
tort, A, fg. 213; and it is found advantageous to use 


Fig. 213. 


the quantity of sulphuric acid here stated, because a solu- 
ble bisulphate of potash is formed, which may be easily 
removed without breaking the retort. Half as much sul- 
phuric acid would effect the decomposition, but it would 
require a higher temperature, and the neutral sulphate 
which forms could with difficulty be removed. The 
change which takes place is thus exhibited : 


(KO, NO,) + 2(HO, SO,)...=...(KO, HO, 2S0,) 
+ (HO, NO;;) 


From what sources is nitrate of potash produced? How may nitric acid 
arise from the oxydation of ammonia? How may nitric acid be made? 


PROPERTIES OF NITRIC ACID. 211 


that is, one atom of nitrate of potash and two of sulphuric 
acid furnish one atom of bisulphate of potash, and one of 
hydrated nitric acid distills over into the receiver, B, which 
is kept cool by a stream of water flowing from 2z into a 
vessel, c c, the waste water passing through led. <A net 
is wrapped over the receiver to distribute the water 
evenly. In this process nitrate of soda may be advanta- 
geously substituted for nitrate of potash. 

Hydrated nitric acid thus produced is a colorless liquid, 
which boils at 248° F’., though this point changes with 
the amount of water in the acid. It freezes at —40°; is 
decomposed into oxygen and nitrogen by being passed 
through a red-hot glass tube. It turns yellow in the sun- 
shine, owing to a portion being decomposed and nitrous 
acid set free, which dissolves in the residue, and gives it 
an orange tint. The nitric acid of the shops (aqua fortis) 
commonly possesses this color, from which it may be 
freed by boiling in a glass vessel. It stains the skin and 
other organic matters yellow, and hence is used in the 
arts of dyeing. Its action on many metalline and other 
combustible bodies is exceedingly violent, ow- Fig. 214. 
ing to the great amount of oxygen it contains. ) 
Poured upon some pieces of copper in a wine- 
glass, over which a bell jar may be inverted 
(Fig. 214), an effervescence takes place, and 
the red fumes of nitrous acid abundantly form, 
Though it is one of the most powerful oxydizing 
agents we possess, it often happens that, in a state of 
great concentration, it will scarcely act on a metal, but 
the addition of a little water causes the action to set in. 

Nitric acid (NVO,;) is a hypothetical or imaginary body 
which has never yet been isolated; the nearest approach 
to it that we know is the strongest aqua fortis. This has 
a specific gravity of 1°521, and consists of one atom of 
hypothetical nitric acid and one of water. Its formula, 
therefore, 1s 


NO; + HO. 
Its molecular constitution probably is 


NO, + . 


What are its properties? When passed through a red-hot tube, what 
happens to it?) Why is commercial nitric acid often yellow? What is the 
action of this acid on the skin and on metallic bodies? What is the near- 
est approach to hypothetical nitric acid? 


O12 SULPHUR. 


It is, as we shall find hereafter, a hydrogen acid. From 
this we see the reason of the circumstance that in the de- 
composition of dry nitrate of lead, described inthis Lecture, 
nitric acid does not make its appearance, but nitrous acid 
and oxygen; for, being a hypothetical body, its atom is 
dissevered in the act of being set free. 

Nitric acid of commerce can be purified by distillation, 
rejecting the first portions which come over, as they con 
tain chlorine, and leaving a portion in the retort contain- 
ing sulphuric acid and fixed impurities. If twelve parts 
are distilled, the first three may be cast aside, and one 
left in the retort; the intermediate eight are pure. ~ 

When it is. in a solution, nitric acid may be diluted by 
the addition of sulphuric acid, and a drop or two of pro- 
tosulphate of iron; a brownish color is produced where 
the two liquids meet. When in a concentrated state, the 
evolution of red fumes, by the action of copper, detects 
it. It also gives a blood-red color with morphia. The 
nitrates deflagrate when ignited with combustible matter, 
a result which may be well shown by grinding together a 
few ounces of nitrate of potash and common sugar, and set- 
ting fire to the mixture. Owing to the solubility of all its 
compounds, nitric acid can not be precipitated. 


LECTURE XLVII. 


SuLtpuur.—atural and Artificial Forms.— Preparation 
of Flowers —Properties of Sulphur.—lIts Vapor.—Ox- 
ygen Compounds of Sulphur.—Sulphurous Acid.—Prep- 
aration.— Properties.— Bleaching Lffects.—Condensa- 
tion to the Liquid State-——LIts Compounds. 


SULPHUR. S=1612. 

Mucu of the sulphur in commerce is derived from vol- 
canic countries, in which it occurs often in a pure and 
crystallized state. Itis one of the most common element- 
ary substances, being found abundantly united with va- 
rious metals, such as iron, copper, lead. In combination 
with lime, baryta, &c., it occurs as sulphuric acid, and is 

Why can not it be isolated? How may it be purified?’ How may it 


be detected? Why can not nitric acid be detected by precipitation? Un- 
der what forms does sulphur naturally occur? 


a 


FLOWERS OF SULPHUR. 913 


also an ingredient of many animal and vegetable prod- 
ucts. 

Sulphur is met with under three different forms: roll 
sulphur, flowers of sulphur, and lac sulphuris. Roll sul- 
phur is an impure variety, which receives its form from 
being cast into cylindrical molds ; the flowers of sulphur 
are formed from the impure brimstone by sublimation ; 
lac sulphuris differs from the foregoing in being of a white 
celor. It is prepared by precipitation from the persulphu- 
ret of potassium by hydrochloric acid. 

The preparation of flowers of sulphur is conducted in 
an apparatus, such as F¥g.215. A is a room, or chamber, 


se 


of 2000 feet capacity ; cis a pan containing sulphur, which 
is melted by the furnace, o s; the vapor passes along z d 
6, and, entering the chamber, is there condensed. ‘The re- 
sulting flowers are removed through the door p. If an 
explosion occurs, when the process commences, it lifts 
the valve e, and the gases escape through the chimney, ¢, 
M M is a shed under which the apparatus is constructed. 
As the iron pan becomes exhausted, new quantities of 
brimstone can be introduced through the door x. 
Sulphur commonly exists as a solid of a yellow col- 
or, and of a specific gravity of 1:99, having neither taste 
nor smell. It melts at 226° IF’. into a pale yellow-colored 
liquid ; but what is very curious, if the heat be raised to 
about 450° F’., it changes to the color of molasses, and be 
comes so thick and tenacious that the capsule in which 
the fusion is carried on may be turned upside down with- 
out the sulphur flowing out. At 600° F. it boils, and, as 


What are its artificial forms? How are the flowers of sulphur made? 
What are the properties of sulphur? What changes may be observed in 
it when melting? 


214 PROPERTIES OF SULPHUR. 


the heat approaches that point, it again becomes fluid ; 
and, as it cools, runs through the same changes again in a 
reverse order. If suddenly quenched in cold water at the 
. low temperature, before it thickens, it solidifies into ordi- 
nary sulphur; but if heated for a time to near 600°, and 
then quenched, it becomes, on cooling, elastic, like India- 
rubber, and may be drawn into long threads ; and in this 
state is sometimes used for taking casts of coins, for by 
keeping a few days it slowly returns to the condition of 
ordinary sulphur. 

When rubbed on a piece of flannel it becomes highly 
electric, assuming the negative state, and at one time was 
used in the making of electrical machines, before the pow- 
ers of glass were discovered. A roll of it held in the 
warm hand emits a crackling sound, the crystals of which 
it is composed separating from one another. It is a bad 
conductor of heat and electricity, crystallizes under two 
different systems, and is, therefore, a dimorphous body, 
one of its forms being an acute rhombic octahedron, and 
the other an oblique rhombic prism. When heated to 
about 300° F. in the open air, it takes fire, and burns 
with a blue flame, emitting a suffocating odor, fumes of 
sulphurous acid gas. It is wholly insoluble in water ; its 
proper solvent is the bisulphuret of carbon. 

The vapor of sulphur is of a deep yellow color, and has 
the high specific gravity of 6°648. In it metallic bodies 

will burn precisely as they do 
, oxygen gas. Dr. Hare has 
j, shown that if a gun barrel be 
heated red hot at the breech, 
and a piece of sulphur drop- 
ped into it, the muzzle being 
closed with a cork, an ignited 
jet of sulphur vapor issues from the touch-hole, in which, 
if a bunch of iron wire be held, it takes fire and burns brill- 
iantly. 

Sulphur has a very extensive range of affinities, uniting 
with most metallic substances in several different propor- 
tions, with hydrogen and also with oxygen. With the 
latter substance it furnishes the following compounds: 


What electrical condition does it assume by friction? What are its 
conducting powers? - Why is it called a dimorphous body? At what tem- 
perature does it take fire, and what is the product of its combustion? 
‘What is the specific gravity of its vapor? Does it support combustion? 
What are the oxygen compounds of sulphur? 


SULPHUROUS ACID. 215 


SOF 619 Oeil bas ea Sc Ome 08s Os ues On3 
their designations are, respectively, 


Sulphurous acid. 

Sulphuric acid. 

Hyposulphurous acid. 

Hyposulphuric acid. ; { 

Sulphureted hyposulphuric acid (acid of Langtois). ¥ 
Bisulphureted hyposulphuric acid (acid of Fordos and Gelis). 


SULPHUROUS ACID. SO2z = 32'146. 
This acid may be formed by burning sul- 


phur in oxygen gas or in atmospheric air; in 
the latter instance the resulting gas is, of 
course, contaminated with nitrogen. The pro- 
cess may be conducted under a bell jar, the 
burning sulphur being placed on a capsule or 
stand. 

But a much better process is to effect the 
partial deoxydation of sulphuric acid by heat- 
ing oil of vitriol with mercury, which deprives it of one 
atom of oxygen, forming an oxide of mercury, which 
unites with one atom of the excess of sulphuric acid pres- 
ent to form a sulphate. For many of the ordinary purpo- 
ses to which sulphurous acid is applied, it may be pro- 
cured by the action of fragments of charcoal heated with 
sulphuric acid. In this case, however, carbonic acid is 
also evolved. When a solution in water is required, the 
gas may be passed directly into that liquid, but if it be nec- 
essary to retain it in a gaseous state, it must be received 
in jars at the mercurial trough, or collected by the meth- 
od of displacement. 

It is, under ordinary circumstances, a transparent and 
colorless gas, having an un- Fig. 218. 
pleasant taste, and the smell : 
characteristic of burning sul- 
phur. It is wholly irrespira- 
ble, and promptly extinguish- 
es alighted taper. Its specific 
gravity 1s 2°222, and, therefore, 
if a stream of it which has been 
cooled by flowing from the 


How may sulphurous acid be made? What is the principle of the pro- 
cess when sulphuric acid acts on mercury or charcoal? What are the 
products in each case? Why must the gas be collected over mercury ? 
‘What are its properties ? ‘ 


| 


216 SULPHUROUS ACID. 


generating flask a, Fig.218, through a bent tube, d,immers- 
ed in a jar of cold water, be conducted to the bottom of an- 
other jar, c, the gas, as it collects, displaces the atmospheric 
air, floating it out of the vessel. This process is of very 
general application in the collection of gases which are 
absorbable by water, and is known under the name of the 
method by displacement. 

In a jar of sulphurous acid thus collected, if a lighted 

Ig. 219. taper be immersed, it is at once extinguished. 
If the jar be inverted over water, the gas is 
speedily dissolved, that liquid taking up about 
thirty-seven times its volume of the gas. If veg- 
etable colors are submitted to its influence, they 
are bleached, but the color is not destroyed as in 
bleaching by chlorine, since it can be restored 
YZ by the action of a stronger acid. 

Sulphurous acid is among the gases one that most read- 
ily takes the liquid form. Tf there be connected with the 
flask from which this gas | is being evolved a bent tube pass- 
ing through iced water in ajar, and the gas, after traversing 
this tube, ~ be conducted into a bottle placed in a freezing 
mixture ae snow and dilute nitric acid, it condenses into 
a colorless fluid of the specific gravity 1:45, which boils 
at 14° F. This fluid is sometimes used to produce in- 
tense cold by its evaporation. 

With bases, this acid forms a complete series of salts, 
the sulphites, which are readily decomposed by the stron- 
ger acids, and are occasionally employed as deoxydizing 
agents, from the circumstance that metallic oxides may be 
reduced by them, their sulphurous passing into the con- 
dition of sulphuric acid. 


What is the method by displacement? To what extent is this acid sol- 
uble in water? Are its bleaching effects permanent? How may it be 
condensed? What are the properties of this liquid? For what purposes 
are the sulphites employed ? 


SULPHURIC ACID. aig 


LECTURE XLVIII. 


Compounps oF SuLPHUR AND Oxyaen.—Sulphuric Acid. 
—The Anhydrous Acid.—lis Affinity for Water —Ger- 
man Oil of Vitriol.—Its Constitution and Uses —Com- 
mon Sulphuric Acid.—Preparation on the Large Scale. 
—Its Chemical Relations—Purification.— Detection.— 
Other Sulphur Acids. 


SULPHURIC ACID. SO; = 40°159. 

Tx1s compound is not alone the most important of the 
acids of sulphur, but also the most important of all acids. 
By the aid of it, nitric, hydrochloric, and many other 
strong acids are made for commercial purposes. In the 
production of carbonate of soda and chloride of lime, im- 
mense quantities of it are consumed. 

Of sulphuric acid we have several varieties, differing 
from each other in the amount of water they contain. 
1st. There is anhydrous sulphuric acid, the formula for 
which has already been given as containing one atom of 
sulphur and three of oxygen. This substance may be 
prepared by submitting the fuming oil of vitriol of Nord- 
hausen to a temperature of about 290° Fahr., when there 
distills over a white substance of a crystalline aspect. It 
fumes in the air, melts at 77° Fahr., is converted into va- 
por at 160°, has an intense affinity for water, in which, if 
it be placed, it hisses like a red-hot iron. It is to be par- 
ticularly remarked, however, that the acid powers of this 
substance are very feebly marked ; it shows little tenden- 
cy to unite with other bodies, and when such combina- 
tions are effected, the resulting substances are different 
from the true sulphates. 

2d. German, or Nordhausen oil of vitriol, HO, SO, + 
SO). 

This substance is prepared by taking green vitriol, and, 
by exposure to heat, driving off its water of crystalliza- 
tion (six atoms), and also a portion of its saline water. If 
the dried powder be placed in a stone-ware retort and 
exposed to a high temperature, there distills over a dark 


What are the properties of anhydrous sulphuric acid, and how is it pre- 
pared? What is the process for preparing the German oil of vitriol? 
What is its appearance ? ‘ r 


218 OIL OF VITRIOL. 


oily liquid; hence the term o7/ of vitriol: this is the sub- 
stance in question. Its formula shows that it is composed 
of two atoms of anhydrous acid united to one of water. 
A considerable quantity of it is used in the arts for dis- 
solving indigo. 

3d. Common sulphuric acid, HO, SO. 

This is the substance which passes in commerce as 
common oil of vitriol. It is made on the large scale by 
burning sulphur with nitrate of potash or soda, and con- 
ducting the sulphurous and nitrous acids which result 
into large chambers lined with lead, in which steam is 
thrown, the bottom of the chamber being covered with 
water. The sulphurous acid takes oxygen from the ni- 
trous acid, reducing it to the condition of deutoxide; but 
this being done in the presence of atmospheric air, which 
fills the chamber, the deutoxide instantly reassumes the 
condition of nitrous acid. The deutoxide, therefore, con- 
tinually transfers oxygen from the atmospheric air to the 
sulphurous acid, and brings it to the condition of sulphuric 
acid, 

After a time the water at the bottom of the chamber 
becomes charged with sulphuric acid; it is then concen- 
trated by drawing off the excess of water in platina or glass 
boilers, and finally assumes the specific gravity 1°845. Itis 
a dense, oily liquid, freezes at —15° and boils at 620°. 

The attraction of common sulphuric acid for water is 

Fig.220. Very intense. If a tube, containing some ether, 
be stirred in a glass (/%g. 220) in which sulphur- 
4, ic acid and water are being mixed, the tem- 
perature rises so high that in a few moments the 
a ether boils. On the same principle, it will re- 
move from most gases which are passed over it 
any water they may contain; and, as we have seen 
in Lect. XII., water may be frozen by taking advantage 
of the rapidity with which sulphuric acid will absorb its 
vapor. Organic substances may also be charred by the 
action of this acid; for example, woody fibre is a com- 
pound of carbon with the elements of water, and when 
acted upon by sulphuric acid, the carbon is set free, the 
acid taking from it a portion of its water. 


For what purpose is it used? What is the process for preparing com- 
mercial sulphuric acid? What are its properties? What illustrations 
may be given of its intense aflinity for water? 


ACIDS OF SULPHUR. 919 


Sulphuric acid of commerce is never pure ; it contains 
sulphate of lead, derived in the process of its manufacture, 
and also, sometimes, arsenic, selenium, and nitrous acid. 
From the first it may be purified by dilution with water, in 
which sulphate of lead is insoluble; but when required 
entirely pure, it must be distilled, the first portions being 
rejected. 

The presence of sulphuric acid may be detected by any 
of the soluble salts of barium, such as the chloride of 
barium, or the nitrate of baryta, the white sulphate of 
baryta precipitating insoluble in water and acids. 

To black woolen clothing this acid communicates a 
reddish stain, removable by being touched with ammonia. 

Besides the compounds just described, we have other 
definite hydrates of sulphuric acid, thus: 


(4) SO; + 2HO. 
(5) SO; + 3HO. 
The fourth of these has a specific gravity of 1°78, and 
crystallizes at 39° Fahrenheit in large and beautiful crys- 
tals. The fifth has a specific gravity of 1°632. 


HYPOSULPHUROUS ACID, S,O, = 48°266, 
has not yet been isolated; one of its salts, the hyposul- 
phite of soda, is extensively used in the Daguerreotype 
process for removing the sensitive coating on the plates. 


HYPOSULPHURIC ACID, S,O5 = 72355, 
is a sirupy liquid of a very acid taste, and is not applied 
to any use. 
Besides these, we have two other acids of sulphur: 


Sulphureted hyposulphuric acid, S305 = 88°475, discovered by Langlois. 
Bisulphureted hyposulphuric acid, S:Os = 104:595, discovered by Fordos 
and Gelis. 


Chemists are now very generally agreed that all these 
compounds are to be regarded as hydrogen acids—a 
striking departure from the Lavoisierian doctrines. They 
have been led to this view by the consideration that no 
well-marked acid exists in which hydrogen is not found; 
that all these sulphur acids possess the same neutralizing 

By what substances is it usually rendered impure? How may it be 
purified? How may it be detected? How may sulphuric acid stains on 
clothing be removed? What other hydrates of this body are there? 
What are the uses of hyposulphurous acid? What other sulphur acids 


are there? What is the nature of the views now held in relation to the 
acids of sulphur, and acids generally. 


220 SULPHURETED HYDROGEN. 


power, though the quantity of oxygen they contain is so 
different. They regard them all as being formed by the 
union of one atom of hydrogen with a series of different 
compound radicals, as the following table shows: 
Sulphurous acid. . .. . . 1+ SO;3. 
Sulphuric acid . . .. . .A+SO;+ 0. 
Hyposulphurous acid . iT S. 
Hyposulphuric acid H-- SO; + SO3,. 
H 


Acid of Langlois ’ eee SO, SO; +S. 
Acid of Fordos and Gelis .. .H+S8S0;+S0; ie i 
Chlorosulphuric acid . . . . .H+SO;-+ Cl. 
Nitrosulphuric acid . . .. .H+SO3;-+NO,. 
Jodosulphuric acid. . . . . .H+S0O; : 


and, extending these views to the constitution of other 
acids generally, an acid is defined to be ‘‘a compound of 
hydrogen with a simple or compound radical, in which the 
hydrogen may be replaced by any other metal.” 


LECTURE XLIX. 


SULPHUR AND PHospHorus.—Sulphureted Hydrogen.— 
Mode of Preparing it—HIts Odor, Acid Relations, and 
other Properties—Extensively used as a Test.— Occurs 
an INature-—Relations to the Animal System.—Bisul- 
phureted Hydrogen.—SELENIUM.—PuHospuorvus.—Pre- 
pared from Bones.—Shines in the Dark.— Action of 
Light.—Combustibility— Compounds with Oxygen. 

SULPHURETED HYDROGEN. AHS=17'12., 

Fig. 221. Tis gas may be easily prepared by the ac- 
tion of hot hydrochloric acid on the native 
sulphuret of antimony pulverized, and may 
be collected over a saturated solution of salt 
or warm water. The action of the materials 
being 
\. 88,8; + 3(HCl)... = ..88,Cl, 4+ 3( HS); 

that is, one atom of the sesquisulphuret of 
antimony and three of hydrochloric acid yield one of the 
sesquichloride of antimony and three of sulphureted hy- 
drogen. 

Sulphureted hydrogen is a colorless and transparent 
gas, having the odor of rotten eg ges. It is absorbed by 


Describe the process for preparing sulphureted hydrogen. What are 
its distinctive properties ? 


SULPHURETED HYDROGEN. 2215 


water readily, that liquid taking up two or three ”*. 
times its volume. Its specific gravity is 1:177. It A 

is combustible, and may readily be burned from a 
jet placed in the flask in which it is being evolved, 
the products of its combustion being sulphurous , 
acid and water; but if the air in which it 1s burn- | 
ed be limited in quantity, water alone is produced 
and sulphur deposited. Its solution in water decom- 
poses gradually by contact with the air, the hydrogen un- 
dergoing oxydation, and the sulphur being set free. It 
has the properties of a weak acid, reddening litmus fee- 
bly, and yields with metallic bases water and sulphurets : 


MO-+ HS...=...HO+ MS. 


many of these sulphurets being insoluble and highly col - 
ored: antimony gives an orange precipitate ; arsenic and 
cadmium, yellow; lead, brown; and manganese, flesh- 
colored. On this principle, the presence of sulphureted 
hydrogen may be always detected : the carbonate of lead, 
for example, is blackened; and hence, white paint ex- 
posed in places in which sulphureted hydrogen is being 
evolved turns dark, and metallic silver tarnishes, and 
finally becomes black. By a pressure of about seventeen 
atmospheres the gas may be liquefied. . 

The action of sulphureted hydrogen on metallic bod- 
ies may be illustrated in a very interesting manner by 
writing on a sheet of paper with a solution of acetate of 
lead, the letters being invisible until exposed to a stream 
of this gas, when they turn black. Its action in producing 
precipitates may be shown by conducting a stream of it 
through a solution of tartar emetic, arsenious acid, or 
acetate of lead. 

Sulphureted hydrogen is sometimes naturally dissolved 
in spring water, constituting the mineral waters of various 
places, as the Virginia Springs. It is also said to be con- 
tained in the brackish water of the mouths of large rivers, 
due, perhaps, to the action of the organic matter they 
contain upon the sulphates existing in the sea. It has 
been thought by some authors that the existence of this 
gas in the air of those places is connected with the fevers 


What are the results of its combustion? What is the nature of the 
precipitates it gives with metallic oxides? How may this action be il- 
lustrated? Is this gas soluble in water? What is the probable cause of 
its occurrence at the mouths of ane rivers ? 

2 


Lad 


222 SELENIUM.——PHOSPHORUS. 


which there prevail. Sulphureted hydrogen is exceed- 
ingly poisonous when respired. 

There is another compound of sulphur and hydrogen, 
the constitution of which is not precisely known, though it 
is usually described as bisulphureted hydrogen, and its 
formula is therefore HS, In its properties it is said to 
have several analogies with the deutoxide of hydrogen. 


SELENIUM. Se = 39°6. 

This element was discovered by Berzelius in certain 
varieties of pyrites. It is a rare substance, analogous, in 
many respects, to sulphur. It burns in the air, forming an 
oxide which exhales the odor of decaying horseradish. 


PHOSPHORUS..- P=15°'7. 

A remarkable substance, first discovered by Brandt, and 
now extensively procured from burned bones, in which it 
occurs as a phosphate of lime. It is found, also, in other 
animal products, being an essential ingredient in fibrin 
and albumen, and also in the brain and nervous matter. 

To procure it, burned 
bones are reduced to pow- 
der, and digested with di- 
lute sulphuric acid; the li- 
quid is strained, mixed with 
powdered charcoal, and, 
when dry, introduced into 
a stone-ware retort, a, Pig. 
223, to the neck of which 
a bent copper tube, J, is at- 
tached, the mouth of which 
dips beneath water. ‘The 
retort being now exposed 
in a furnace to a white heat, 
half the phosphoric acid in 
the mixture is deoxydized 
by the charcoal, carbonic oxide gas escaping, and phospho- 
rus distilling over. 

Phosphorus is commonly transparent and colorless. 
When exposed to the light it turns of a deep red, and this 
takes place in a vacuum, or in gases which have no action 
on the phosphorus. In lustre and general appearance it 


What other compound of sulphur and hydrogen is there? What is se- 
lenium? From what source is phosphorus derived? 


PROPERTIES OF PHOSPHORUS. 223 


has a waxy aspect. Exposed to the air it smokes, and in 
a dark place shines—a property from which its name is 
derived. During this slow oxydation it exhales an odor 
much resembling that experienced when an electrical ma- 
chine is in high activity. At 32° it is brittle, at 113° it 
melts, at 572° it boils, distilling over unchanged, if oxy- 
gen be absent. But in the air it takes fire and burns at 
about 120°, with evolution of flakes of anhydrous phos- 
phoric acid. Its specific gravity is 1°77. 

From the intense affinity which phospf orus has for oxy- 
gen, it requires to be kept under the surface of water. 
It is met with in commerce in the form of small sticks, a 
form given to it by melting it in glass tubes under warm 
water, and pushing the resulting cylinders out as soon as 
they have set. If kept in an opaque bottle it is white, but 
it slowly turns more or less red on exposure to the day- 
light. 

From the facility with which it takes fire, it is necessary 
to handle it very carefully, and to avoid keeping it in con- 
tact with the warm hand too long. A few particles of 
dry phosphorus placed between two pieces of brown pa~ 
per and rubbed with a hard body, take fire and burn fu- 
riously as soon as the papers are separated. It is upon 
this principle that it will readily inflame by the heat of 
friction, that its useful application in the manufacture of 
friction matches depends. In chlorine, or the vapor of 
bromine and iodine, it takes fire spontaneously. 

There are several compounds of phosphorus and oxy- 
gen, as follows: 7 


DEMOS Ral EM OLS ta £40 Selma oot 6 P. 
These are respectively 


Oxide of phosphorus. Phosphorous acid. 
Hypophosphorous acid. Phosphoric acid. 


What remarkable property does this body possess? Why is phosphorus 
to be kept under the surface of water? What is the action of light upon 
it?’ What useful avpiication is made of its ready combustibility? How 
many compour.us of phosphorus and oxygen are there ? 


224 PHOSPHORUS AND OXYGEN, 


LECTURE L. 


Comrounps or PuHospHorus AND OxyGEeNn.—Ozxide of 
Phosphorus——Preparation of—lHypophosphorous and 
Phosphorous Acids—Phosphoric Acid—Three States 
of Hydration.—Properties of these three Acids.— Their 
Salts. — Phosphureted Hydrogen.— Spontaneously In- 
flammable and Non-inflammable Varveties—CUuLORINE. 
—Preparation of—LIts Relations to Combustion and 


Respiration. 
OXIDE OF PHOSPHORUS. P;0=55:113. 
Fig. 224. Tus oxide may be formed by causing 


a stream of oxygen gas, from the tube a, 
Fig. 224, to be directed upon phospho- 
rus under hot water in a glass, 6. A 
brilliant combustion under the water is 
the result, with the production of phos- 
phoric acid and of a red powder, which 
is the substance in question. 

GS) HYPOPHOSPHOROUS ACID, P,;O=39°413, 
is very little known; it is formed when phosphorus is 
boiled in alkaline solutions. 

PHOSPHOROUS ACID, PO, = 55439, 
is formed during the slow combustion of phosphorus in the 
air; it may also be produced by acting on the sesquichlo- 
ride of phosphorus with water. ‘The solution of this acid 
is sometimes used as a deoxydizing agent. 
PHOSPHORIC ACID. P,O5=71°465. 
Anhydrous phosphoric acid is formed 


Fig. 225. 
O ~ 


ygen gas (fg. 225). It condenses 1m 
white flakes of a snowy appearance, and 
possesses an intense affinity for water, in 
which, if placed, it hisses like a red-hot 
iron. It can scarcely be said to possess 
£25 acid properties. Until it has united with 
water, those properties are very feebly developed. 
“How is oxide of phosphorus made? What is its appearance? How 


are hypophosphorous and phosphorous acids produced? Under what *ir- 
eumstances is anhydrous phosphoric acid produced ? 


when phosphorus burns in dry air or ox-~ 


ACIDS OF PHOSPHORUS. 225) 


- With water, phosphoric acid unites in three propor- 
tions, producing 
Monobasic phosphoric acid . . ee FTO, or H+ P2O6. 
Bibasic a « e 6« P205--2HO, or 2H + P2O7 
Tribasic = “« . . P205-+3HO, or 3H + P2Osz. 
These acids also have the names of metaphosphoric, pyro- 
phosphoric, and common phosphoric acids respectively. 
Hither of them may exist in solution with water. 

Metaphosphoric, or the monobasic phosphoric acid, may 
be obtained by dissolving phosphorus in dilute nitric 
acid, evaporating, and exposing the residue to a red heat. 
It may also be obtained by dissolving the anhydrous acid 
in water, evaporating and igniting it. In both these cases 
a transparent body, like ice or glass, is produced ; hence 
called glacial phosphoric acid. It contains one atom of 
water, which can not be removed from it by heat. 

Monobasic phosphoric acid is characterized by giving 
a white granular precipitate with nitrate of silver ; it also 
coagulates albumen, producing white curds. If kept in 
a solution of water, or boiled with it, it passes into the 
tribasic state. 

Pyrophosphoric, or bibasic phosphoric acid, may be 
obtained by heating the common phosphoric acid to 
417° F. for some time. In solution it neither precipi- 
tates silver nor coagulates albumen, but its salts yield, 
with silver, a flaky white precipitate. Like the former, 
this turns into the tribasic acid by boiling with water. 

Common, or the tribasic phosphoric acid, may be ob- 
tained from bone earth by the action of oil of vitriol, 
which yields a precipitate of sulphate of lime; or, more 
easily, by boiling a solution of the anhydrous phosphoric 
acid. In solution it neither precipitates silver nor coagu- 
lates albumen, but its salts yield a Canary-yellow precip- 
itate with the nitrate of silver. By exposure to a low 
heat it becomes bibasic, and to a red heat, monobasic. 

These hydrogen acids of phosphorus give rise to a 
very extensive and complex class of salts, according to 
the extent to which their hydrogen is replaced by metal- 
lic bodies. ‘Thus, the monobasic phosphoric acid can 
yield only one series of salts, in which all its hydrogen is 


How many compounds does it yield with water? How is metaphos- 
phoric acid made? What is glacial phosphoric acid? What are the 
properties characteristic of monobasic, bibasic, and tribasic phosphoric 
acids respectively? How many series of salts can each yield? 


- 


226 PHOSPHURETED HYDROGEN. 


replaced by a metal; but the bibasic can yield two differ- 
ent series, according as the metal replaces one or both 
atoms of base; and the tribasic can yield three different 
series, according as one or two or all three of its hydro- 


gen atoms are replaced. 
PHOSPHURETED HYDROGEN, P,H; = 344, 


may be made by boiling phosphorus in a strong solution 
of lime or potash in a retort, a, Fig. 226, the neck of 


Fig. 226. 


which dips beneath the surface of water, a few drops of 
ether being previously put into the retort. As the bub- 
bles of gas break on the water, they take fire, burning 
with a bright yellow light, and there ascends through the 
air a ring of gray smoke, which dilates as it rises, and 
exhibits a curious rotatory movement of its parts. This 
gas, also, may be made by bringing the phosphuret of cal- 
cium in contact with water. 

Phosphureted hydrogen is a colorless gas, exhaling a 
peculiar odor, like garlic, and, when burning, produces 
phosphoric acid and water. It exists under two forms: 
1st. Spontaneously inflammable; 2d. Not spontaneously 
inflammable. It is said that the first may be changed into 
the second by small quantities of the vapor of ether, oil of 
turpentine, &c., and the second into the first by the addi- 
tion of a minute quantity of nitrous acid. 


CHLORINE. Cl=35-47. 


Chlorine is found abundantly in nature in union with so- 
dium, forming common salt, a substance which, for the 
most part, gives to the sea water its salinity, and consti- 


Describe the preparation of phosphureted hydrogen. What are the 
properties of phosphureted hydrogen? How may its two forms be con- 
verted into each other’? In what substances does chlorine chiefly occur? 


PREPARATION OF CHLORINE. be | 


tutes the deposits of rock salt. It is, therefore, an abund- 
ant substance. 

Chlorine is best made by the action of hydrochloric acid 
on peroxide of manganese : 


MnO,+ 2HCl...=... MnCl 4+ 2HO + Cl; 


that is, one atom of peroxide of manganese and two of 
hydrochloric acid yield one atom of the chloride of man- 
ganese, two of water, and one of chlorine. Half the chlo- 
rine is, therefore, given off as chlorine gas, and the other 
half remains as chloride of manganese. 

Chlorine gas being very soluble in cold water, and act- 
ing with great energy on mercury, it can = Fig. 227. 
neither be collected at the water nor mercu- 
rial trough ; but, having a specific gravity of 
2°470, we are able to collect it by the meth- 
od of displacement, as shown in J/g. 227, | 
It may, however, also be collected over warm 
water or a saturated solution of common salt. 

When chlorine is required in a state of dryness, it may 
be obtained by an apparatus like that represented in Fvg. 
228. a is the retort containing the hydrochloric acid and 


Fig. 228. 


SY S533) = 


Fs 


manganese. It is connected with a small receiver, 34, 
which retains part of the water which the gas may bring 
over; this, again, is connected with a chloride of calcium 
tube, c, which effects the perfect drying of the gas. 
Chlorine is a gas of a pale, yellowish green color. It may 


How may it be formed? What are its properties? How is it pro- 
cured in a state of dryness? 


228: PROPERTIES OF CHLORINE. 


be liquefied by a pressure of four atmospheres. A taper 
immersed in it burns for a few minutes with a dull red 
flame, emitting volumes of smoke, due to the fact that the 
Fig.229. hydrogen of the flame continues to burn or unite 
with the chlorine, forming hydrochloric acid; but 
the carbon, Having little affinity for chlorine, is 
set free in an uncombined state, as lampblack. 
Powdered antimony, or thin brass leaf, plunged 
:\ in this gas, becomes incandescent, and burns, pro- 
g) ducing a chloride. A piece of phosphorus im- 
mersed in it takes fire at common temperatures, 
and burns with a pale flame. The smell of chlo- 
rine is disagreeable, and its effect, even in a diluted state, 
suffocating. It irritates the air passages of the lungs, 
producing hiccough and an unpleasant expectoration. 


LECTURE LI. 


CHLORINE, CONTINUED.—Bleaching Properties.— Combus- 
tion of Hydrocarbons.—Disinfecting Qualities.—Com- 
pounds with Oxygen. — Properties of Hypochlorous, 
Chlorous, and Chloric Acids —Quadrochloride of Nitro- 
gen.—Hydrochloric Acid.— Preparation in the Gaseous 
and Liquid States. 


Tue most valuable property of chlorine is its power of 
discharging vegetable colors, on which is founded its ap- 
plication in the arts of bleaching and calico printing. This 
Fig. 930, property may be illustrated in many ways. By 

(7qz pouring a solution of litmus or indigo through a 
funnel, a, Fig. 230, into a flask, 6, containing chlo- 
\ rine gas, the decoloration takes place instantly, or, 

\b if the color is not completely discharged, it will be 
) found, in a short time, to disappear. The same 
takes place when a solution of chlorine in water is 


used. 
The peculiarities of chlorine ‘in supporting combustion 
are remarkable, when compared with those of oxygen 


What are its relations in the combustion of a taper, and how does it act 
on certain metals and phosphorus? What is its effect on the animal 
system? Of the properties of chlorine, which is the most valuable? How 
may it be illustrated ? 


PROPERTIES OF CHLORINE. 229° 


gas. A piece of paper, Fig. 231, dipped in oil j,,, 
of turpentine, takes fire in a moment at com- _... 
mon temperatures, when placed in a jar of chlo- 
rine, and, as we have seen, phosphorus and sev- 
eral of the metals undergo spontaneous ignition 
in the same manner. These phenomena depend 
on the intense affinity which chlorine has for elec- | 
tro-positive bodies, but it is very remarkable that \ 
it seems to have little disposition to unite with 
carbon. As in the burning of a taper, so in this exper- 
iment with turpentine, it is the hydrogen which burns, and 
the carbon is evolved in clouds of smoke. 

Chlorine is also used by physicians for the purpose of 
destroying miasmata, and the effluvia of sick-rooms or oth- 
er places. It is necessary, from its irrespirable qualities, 
to disengage it slowly and with caution where patients 
are present. The chlorides of soda and lime are common- 
ly used. 

Free chlorine may be detected by its smell, its bleach- 
ing action on indigo solution, and giving a white, curdy 
precipitate with the nitrate of silver. Its solution in water 
is readily made by introducing a small quantity of water 
into a bottle full of chlorine, agitating it, and opening the 
mouth of the bottle from time to time under water; the 
gas being gradually absorbed, the bottle becomes full of 
water, which, of course, contains its own volume of chlo- 
rine. ‘This solution decomposes in the sunshine, evolying 
oxygen gas, the water being decomposed. With oxygen 
chlorine unites in several proportions, producing, 


Gt: 2s. ClO. 2s CLO, 4. GLO. 
They are designated 
Hypochlorous acid. Chloric acid 
Chlorous acid. Perchloric acid. 
HYPOCHLOROUS ACID. ClO = 43°483. 
Hypochlorous acid may be obtained by agitating the 
red oxide of mercury, suspended in water, with chlorine. 
If a strong solution of it be placed in an inverted tube, 
and pieces of dry nitrate of lime be added, the gas is dis- 


231, 


Mes" ase SD). 


W hat is the cause of the clouds of smoke deposited when carburets of 
hydrogen burn in chlorine gas? For what purpose is chlorine used by 
eeeiciens | How may chlorine be detected? How may a solution of it 

e made? What compounds of chlorine and oxygen are known? Ilow 
is hypochlorous acid made, and what are its propertics ? 


230 ACIDS OF CHLORINE. 


engaged, and rises to the top of the tube. It is of a deep- 
er color than chlorine, bleaches powerfully, and, by a 
slight elevation of temperature, explodes, evolving two 
volumes of chlorine and one of oxygen gas. 

The bleaching compounds are compounds of chlorides 
and hypochlorides. They are easily decomposed by 
acids. ~“[hus, when chloride of lime is to be used for dis- 
infecting purposes, it is merely required to expose it with 
water to the carbonic acid of the air, or to add a little of 
it, from time to time, to a vessel containing dilute sulphur- 
ic acid. 

CHLOROUS ACID, ClO, = 67°522, 
may be made by cautiously acting on small quantities of 
chlorate of potash with sulphuric acid. It is a yellow 
gas, which explodes furiously from very slight causes, the 
warmth of the hand being often sufficient to give rise 
to a violent action. It contains two volumes of chlorine 
and four of oxygen, condensed into four volumes. It may 
be conveniently made by operating on a few grains of the 
chlorate in a test tube. If into a glass, a, Fig. 
232, containing water, a small quantity of chlo- 
rate of potash is placed, and upon it a few frag- 
ments of phosphorus, and sulphuric acid be 
= poured through a funnel, 4, so as to act on the 
chlorate, chlorous acid is set free; it communi- 
cates a golden yellow color to the water, and 
as each bubble passes by the phosphorus it sets it on fire, 
furnishing a beautiful instance of combustion under water. 


CHLORIC ACID, ClOs = 75°535, 

may be made by decomposing the chlorate of baryta by 
sulphuric acid, and evaporating the solution. It is a yel- 
low, viscid acid: a piece of paper dipped in it is set on 
fire. It does not bleach. It forms salts, one of which, the 
chlorate of potash, is of considerable importance, and is 
used for the preparation of oxygen. A few grains of the 
chlorate of potash, ground in a mortar with a pinch of 
flowers of sulphur, explodes incessanily during the tritu- 
ration. 


Fig. 232. 


PERCHLORIC ACID. ClO; =91°561. 
The perchlorate of potash forms along with the chloride 


What are the properties of chloric acid? How may the combustion of 
phosphorus under water be produced by it? How is chloric acid made? 


HYDROCHLORIC. ACID. 231 


of potassium when one third of its oxygen is expelled 
from chlorate of potash; the two salts may be separated. 
from each other by boiling in water, the perchlorate crys- 
tallizing on cooling. From this perchloric acid may be 
obtained by distillation with an equal weight of oil of vit- 
riol, mixed with half as much water. It may be obtained 
in the form of a white crystalline mass, very deliquescent, 
and its solution is sometimes used as a test for potash, 
with which it gives a sparingly soluble salt. The solu- 
tion fumes in the air, has a specific gravity of 1°65, and 
does not possess bleaching properties. 


CHLORINE AND NITROGEN. 

These substances unite, forming an oily liquid, when a 
warm solution of sal ammoniac is exposed to chlorine gas. 
The resulting body is regarded as a quadrichloride of 
nitrogen (JVC/,). By its violent explosions, several emi- 
nent chemists have been seriously injured. The mere 
contact of oily matter produces a detonation. 


CHLORINE AND HYDROGEN. 
HYDROCHLORIC ACID. HCl.= 36°47. 

This acid, called also muriatic acid, is easily prepared 
by placing in a flask six parts of common salt and ten 
parts by weight of oil of vitriol, mixed with four of water, 
the mixture being suffered to cool before it is introduced. 
On heating the mixture, hydrochloric acid is evolved, 
which passes along a bent tube into a bottle containing 
six parts (by weight) of water. The end of the tube dips 
but a very short distance beneath the surface of this wa- 
ter, so that if the liquid should rise it may be received 
into a ball blown upon the tube, and the extremity of the 
tube becoming uncovered, atmospheric air may pass into 
the interior of the flask. At the close of the process, the 
liquid in the bottle, which should be constantly surrounded 
by ice water in a small tank, more than doubles its volume, 
and is a pure solution of hydrochloric acid. The action is 


NaCl + 2(HO, SO;)... =... HCl + (NaO, HO,2S0;); 
> that is, one atom of chloride of sodium and two of sul- 


phuric acid yield one atom of hydrochloric acid and one 
of the bisulphate of soda. 


How is perchloric acid prepared, and for what purpose is it used? 
What are the properties of the chloride of nitrogen? How is hydrochloric 
acid made? 


232 HYDROCHLORIC ACID. 


From the liquid thus produced, or from the commercial 
muriatic acid, by heating in a flask, pure hydrochloric 
acid gas may be obtained; it may also be less advanta- 
geously procured by the direct action of strong oil of vit- 
riol on common salt, the reaction in this case being 

NaCl + HO, SO,;...=...HCi+ NaO, SO. 

Pure hydrochloric acid is a transparent, colorless gas, 
possessing powerful acid qualities, very absorbable by wa- 
ter, which liquid takes up several hundred times its own 
volume of the gas ; it fumes in moist air, and has a pungent 
odor. Ifa dry Florence flask (F%g.233) be Fig. 233. 
filled with it by the process of displacement, 
and the mouth of it opened under the surface 
of cold water, the water rushes up into the , 
flask, absorbing the gas with great violence. 
The specific gravity of hydrochloric acid is © 
1:284. It contains equal volumes of its constitu 
ted without condensation. 


LECTURE LII. 


CHLORINE, CONTINUED.—Production of Hydrochloric Acid 
by Light.—Action of Hydrochloric Acid on Metallic 
Protoxides—Muriatic Acid Solution.— Detection of Hy- 
drochloric Acid.— Nitromuriatic Acid.—lopinE.—Sour- 
ces of.— Preparations and Properties.— Tests for Iodine. 
—TIts Action on Starch.— Hydriodic Acid.— Oxygen 
Compounds of Iodine. 


Pure hydrochloric acid gas is also obtained when a 
mixture of chlorine and hydrogen, in equal proportions, 
is exposed to the light. In the dark these gases appear 
to have no disposition to unite, but if they be placed in a 
flask covered over with a wire screen, and a beam of the 
sunlight reflected upon them from a looking-glass, a vio- 
Jent explosion ensues and hydrochloric acid is formed. 

I have found that, in this remarkable experiment, the « 
action is chiefly due to the chlorine, which, from being in 


How may the gas be procured? What are the properties of hydro- 
chloric acid gas? How may its affinity for water be proved? What is 
its constitution? What is the action of sunlight on a mixture of chlorine 
and hydrogen? To which of these bodies is this action due? ~ 


PROPERTIES OF HYDROCHLORIC ACID. 233 


f passive, assumes an active state by exposure to rays of 
an indigo color. It may be thrown into the same condi- 
tion in many other ways; for example, by the contact of 
spongy platina. Moreover, when chlorine by itself has 
been exposed to the sun, it gains the quality of uniting 
more easily with hydrogen than chlorine which has been 
made and kept in the dark. 

When hydrochloric acid is brought in contact with 
metallic oxides, decomposition of both ensues, and metallic 
chlorides are formed, thus: 


MO Oe Cr ee ss MCE. ECHO, 
or, s MOP aC Oly rn wee IMA Clg. OLE 
that is, one atom of a metallic protoxide with one atom 
of hydrochloric acid yields one atom of a protochloride of 
the metal and one of water. But, in the case ofa sesqui- 
oxide, one atom of it with three of hydrochloric acid 
yield one atom of the metallic sesquichloride and three of 
water. 

The constitution of hydrochloric acid, and its Fig. 234. 
action on metallic oxides, may be strikingly illus- j 
trated by taking a flask, & (Fig. 234), filled with 
it, in a perfectly dry state, and allowing the perox- 
ide of mercury, in fine powder, to fall through it. 
The bichloride of mercury, corrosive sublimate, 
instantly forms, and drops of water make their ap- 
pearance on the sides of the flask. 

It is under the form of a solution in water, as liquid 
muriatic acid, or spirit of salt, that hydrochloric acid is 
chiefly used. The mode of obtaining it has been described 
in the last Lecture. This liquid, when concentrated, has 
a specific gravity of 1:21, and contains 42 per cent. of acid. 
It smokes in the air, and reddens blue litmus powerfully. 
The commercial acid is usually of a yellow color; it con- 
tains chloride of iron, derived from the iron vessels from 
which it is distilled. It also often contains sulphuric acid, 
chlorine, sulphurous acid, tin, or arsenic, and is, therefore, 
best prepared by the process described, which yields it in 
perfect purity. 

Hydrochloric acid may be detected by yielding, when 


W hat is the action of hydrochloric acid on metallic oxides? What are 
the products of the action of hydrochloric acid on peroxide of mercury ? 
What are the properties of liquid muriatic acid? What are its im- 


purities ? 
U2 


234 NITROMURIATIC ACID. 


in a free state with ammonia, dense white clouds 
of sal ammoniac. If two glasses, one filled 
with this acid, and the other with ammonia, be 
brought near each other, a white cloud forms be- 
tweenthem. A glass rod, a (fig. 236), dipped 
inammoniamay be used forthe same __j; 
purpose. With nitrate of silver hydrochloric 
acid yields a white chloride of silver, which 
turns black in the light, being the same pre- 
cipitate given under the same circumstances 
by free chlorine. From this latter substance 
it may be distinguished by litmus water, which 
is bleached by chlori ine, and reddened by hrdternitg ic acid. 
Nitromuriatic acid, or aqua regia, is formed by adding 
to hydrochloric acid one half or a third of its volume of 
nitric acid. The nitric acid, furnishing oxygen tothe hy- 
drochloric acid, forms water, and chlorine, with nitrous 
acid, is set free in the solution. Aqua regia is used as a 


solvent for platina and gold, a result which may be illus- 


trated by placing a sheet of gold leaf in the mixture. 


IODINE. J=126°57. 

Iodine chiefly occurs in the products of the sea, being 
found in sea-weed, sponge, &c.; also in certain brine 
springs, and in some ores of silver and zine. 

It may be obtained by lixiviating the ashes of sea-weeds, 
and evaporating the solution until no more crystals are de- 
posited. The residual liquor is then acted upon by sul- 
phuric acid, and subsequently heated with peroxide of 
manganese, ina leaden retort, a b ¢ (Mig. 237, page 235), 
the iodine distills over into the receivers, d. 

It is a solid substance, of a deep blue or black appear- 
ance, with a semi-metallic lustre, communicates to the 
skin a fugitive yellow stain, and exhales an odor like that 
of sea beaches. It crystallizes in rhomboidal plates, is 
brittle, and has a specific gravity of 4948. At 225° it melts, 
and boils at 347°, exhaling, even at moderate tempera- 
tures, a splendid purple vapor, from which its name is de- 
rived. The specific gravity of this vapor is 8°707; it is, 
therefore, one of the heaviest gaseous bodies known. 


How may hydrochloric acid be detected? What is the preparation 
and property of nitromuriatic acid? From what source is iodine procured ? 
What is the method of its preparation? Whatis its appearance? What 

is the color of its vapor? From what circumstance is its name derived? 


ae 


IODINE. 235 


== Fig. 237. 


Iodine supports combustion much in the 
same manneraschlorine. A jar, a (Ig. 238), 
containing a few grains of it, placed in a small 
sand bath, 6, and warmed by a spirit lamp, c, 
may be easily filled with its dense vapor, the 
atmospheric air floating out before it. In this 
vapor if a lighted taper is plunged, it exhibits 
a retarded combustion; but a piece of phos- 
phorus, introduced on a spoon, takes fire and burns. In 
the same manner, if a quantity of iodine 
be placed in a small capsule, and upon it 
a fragment of dry phosphorus (fg. 239), 
spontaneous ignition ensues, with the ey- 
olution of phosphoric acid, and the vapor 
of iodine, iodide of phosphorus remaining 
in the capsule. 

In water, iodine is but slightly soluble, 
that liquid taking up 7,),th part of its 
weight and assuming a brown color. Alcohol dissolves 
it freely, forming tincture of iodine. In solutions of the 
iodides iodine may be dissolved. 

With many substances iodine gives characteristic reac- 
tions. The iodide of potassium, with the acetate of lead, 


What are its relations as respects combustion? Is it soluble in water 
and alcohol? 


236 HYDRIODIC ACID. 


yields a golden yellow precipitate ; with the bichloride of 
mercury, a fine scarlet-colored biniodide. This substance 
possesses the singular quality that, if dried and sublimed 
in a tube, it yields crystals of a brilliant yellow aspect, 
which become red on being simply touched with a hard 
body. With a solution of starch free iodine yields a deep 
blue color, the solution becoming colorless if heated, but 
the blue color returning on cooling, provided the temper- 
ature has not been carried to the boiling point. If a po- 
tato be cut in two, and a little tincture of iodine poured 
on the surface, innumerable blue specks make their ap- 
pearance, each corresponding to the position of a granule 
of starch. Starch and free iodine will, therefore, mutually 
detect the presence of each other. 


HYDRIODIC ACID. HI=127°57 

Hydriodic acid gas may be obtained by dissolving in a 
solution of iodide of potassium as much iodine as it will 
* hold, adding small pieces of phosphorus, and warming the 
mixture. A colorless transparent gas is evolved, which 
fumes in the air, and may be collected over mercury. Its 
specific gravity is 4°384. It has the general relations of 
hydrochloric acid, and, like it, is very soluble in water. 

Fig. 240. A gelitcn of hydriodic acid in water may 
be made by passing a stream of sulphureted 
hydrogen from a flask, a (7g. 240), through 
FE|, water, 5, in which thet substance is suspend- 
ed. ‘The'acid forms and sulphur is deposited : 


dt pals 5. 2 = feat gtd de 


With nitrate of silver this acid yields a pale yellow pre- 
cipitate, the iodide of silver. This is the substance which 
forms the basis of the remarkable compound used in the 
Daguerreotype. In that case it is formed by holding a 
plate of pure, polished silver in the vapor of iodine; the 
plate tarnishes and turns yellow, and, if set in the sun- 
shine, turns promptly of a deep olive black. 

Iodine yields two oxygen acids, iodic (1O;) and peri- 
odic acid (1O,). With nitrogen, also, it gives NI,, char- 
acterized, like the analogous compound of chlorine, by the 
facility with which it explodes. 


How may it de detected? In what manner is hydriodic acid made ? 
What is the simplest method of obtaining a solution of it? What is the 
precipitate it yields with nitrate of silver? What are the oxygen com- 
pounds of iedine ? 


BROMINE. 237 


LECTURE LIII. 


Bromine — Fivorine.— Bromine.—Sources of—Proper- 
ties.— Compounds of —F.uorine.—Hydrofluoric Acid. 
—Its Properties and Action on Glass —Carson.—Allo- 
tropic Forms of —Preparation of some of those Forms. 
— Diamond.— Oxygen Compounds of Carbon.—Carbon- 
ic Oxide. 

BROMINE. Br=78°'39. 

BROMINE occurs in sea water, and also’'to a more consid- 
erable extent in certain brine springs both in America and 
Europe. From these it may be obtained by evaporating 
the water until the salt solution is concentrated, and after 
the chloride of sodium has crystallized from the liquor, 
passing through it a current of chlorine gas, the solution 
turning yellow as the bromine is set free. It is next agita- 
ted with sulphuric ether, which carries to the surface all 
the bromine. This is then acted on by potash, which gives 
a mixture of bromate of potash and bromide of potassium. 
On ignition, oxygen is expelled, and the whole converted 
into the latter salt, from which the bromine may be distilled 
by the aid of peroxide of manganese and sulphuric acid. 

It is a liquid of a deep blood-red appearance, solidify- 
ing at —4° I*., and boiling at 113° F. Its specific gravity 
is 2°99. It exhales an orange vapor, and is commonly 
kept beneath the surface of water. Its smell is very dis- 
agreeable, a circumstance from which its name is derived, 
Like chlorine, it bleaches, and in all its relations possesses 
a general resemblance to that substance. A lighted taper 
burns for a short time in its vapor with a greenish flame. 
Phosphorus burns spontaneously in it. 

Bromine yields a hydrogen acid (HBr), hydrobromic 
acid, and with oxygen, bromic acid (brO;). In their gen- 
eral properties these bodies resemble the corresponding 
compounds of chlorine. The bromide of silver is much 
more sensitive to light than either the chloride or iodide. 


FLUORINE, F=— 18°74, 
is found in combination with calcium, as the fluoride of 


From what s¢urce is bromine obtained? What are the properties of 
bromine, and to what bodies has it a close analogy ? 


238 FLUORINE. 


calcium, or fluor spar. It occurs also in the topaz and 
other minerals. In the enamel of teeth and in bones it has 
been detected, especially in fossil bones, which sometimes 
contain as much as ten per cent. of fluoride of calcium. 
The special properties of fluorine are as yet unknown, 
for it has not been isolated. Various attempts have been 
made at different times, but without satisfactory results. 
It possesses an intense affinity for electro-positive bodies, 
» and gives rise to a series of compounds resembling those 
of chlorine, iodine, &c. It does not unite with oxygen. 


HYDROFLUORIC ACID. HF =1974. 

This energetic acid may be obtained by decomposing 
fluoride of calcium by sulphuric acid in a vessel of platina 
or lead, the vapors being conducted into a metallic re- 
ceiver kept at a low temperature. The action is 


CaF + HO, SO;...=... CaO, SO; + AF. 


It is a smoking liquid, which acts powerfully on the 
skin, boils at a temperature of a little above 60° F., and 
possesses the remarkable quality of corroding glass. 

If a piece of glass be coated over with a thin film of, 
bees’ wax, and letters or other marks made through the 
wax to the glass with a pointed implement, on setting it 
over a vessel of lead or tin in which, from a mixture of 
fluor spar and sulphuric acid, hydrofluoric acid is escaping 
in vapor, the glass is deeply etched on all those parts 
which have been uncovered, as is seen when the wax is 
removed. Liquid hydrofluoric acid may be employed 
for the same purpose, but the letters are not so visible as 
when the vapor is used. 


CARBON. C= 6°04. 

This, which is one of the most interesting and import- 
ant of the elementary bodies, occurs under many differ- 
ent natural forms. It is an essential ingredient in the 
structure of all animal and vegetable beings ; it is found 
in various states in the air, the sea, and the crust of the 
earth. 

The striking peculiarity of carbon, which at once arrests 
our attention, is the different allotropic conditions under 
which itis presented. This substance may be said to yield 


Are the special properties of fluorine known? How is hydrofluoric acid 
made? What remarkable quality does it possess? From what sources 
may carbon be procured? What is its most striking property ? 


FORMS OF CARBON. 239 


in itself a whole group of elementary bodies. Amon 
these might be enumerated, (1.) Diamond, which crys- 
tallizes in octahedrons, is transparent, incombustible, ex- 
cept in oxygen gas, and the hardest body known; hence 
its use in cutting glass. (2.) Gas-carbon, which, unlike 
diamond, is a good conductor of electricity, and is opaque, 
(3.) The various forms of charcoal, anthracite coal, and 
coke. (4,) Plumbago, which has a metallic lustre, is 
opaque, and so soft and unctuous that it is used to relieve 
the friction of machinery. (5.) Lampblack, a powerful 
absorbent of light and heat, and possessing such strong 
affinity for oxygen that it can take fire spontaneously in 
the air. 

Other forms of carbon might be cited; these, however, 
are enough to establish the fact that this single body fur- 
nishes varieties which differ more strikingly from each 
other than many different metallic bodies. 

Charcoal is made by the ignition of wood in close ves: 
sels, the volatile materials being dissipated and the Fig2«i. 
carbon left. The nature of the process may be il- 3 
lustrated by taking a slip of wood, b, Fig. 241, and 
placing its burning extremity in atest tube, a. This 
retards the access of the surrounding air, ‘and, as the 
combustion proceeds, a cylinder of charcoal is left. 

” Fig. 242. Lampblack is formed on 
a similar principle. In the 
iron pot, a, Fig. 242, some 
pitch or tar is made to boil, 
a small quantity of air being ad- 
mitted through apertures in the 
brickwork. Imperfect combustion 
takes place, the hydrogen alone 
burning, the carbon being carried 
as a dense cloud of smoke into 
the chamber 6 ¢ by the draft. 
In this there is a hood, or cone, of 
es -coarse cloth, d, which may be 
raised or jagieed ne apulley. The ‘sides of the chamber 
are covered with leather, and on these the lampblack 
collects. 
Diamond is the purest form of carbon. Its specific 


Mention some of its allotropic forms. How are charcoal and lampblack 
made? 


‘940 CARBONIC OXIDE. 


gravity is 3:5: it exhibits a high refractive and dispersive 
action upon light. Charcoal possesses, in consequence of 
its porous structure, the quality of absorbing many times 
its own volume of different gases. Ivory black, which is 
made by the ignition of bones in close vessels, has the val- 
uable quality of removing organic coloring matters from 
their solutions: a property which may be shown by filter- 
ing a solution of indigo through it. In all its forms, car- 
bon seems to be infusible, but when burned in air or an 
excess of oxygen, they all give rise to carbonic acid gas. 
It combines directly with several of the metals, yielding 
carburets. With oxygen it gives two compounds, 


COM se CO. 


designated respectively as carbonic oxide and carbonic 
acid. 
CARBONIC OXIDE, CO = 14-053, 

is produced when carbon is burned in a limited supply 
of oxygen, or when carbonic acid is passed over red-hot 
iron, or over red-hot carbon. In these cases the actions 
are: 

COMBO es == viele 

COit+Fe...=...CO+Ffe0. 


In the first the carbonic acid unites with one atom of 
carbon, and yields two of carbonic oxide; in the’second, 
it loses one atom of oxygen to the iron and yields one of 
carbonic oxide. It may also be prepared by heating ox- 

Fig. 243. alic acid with oil of vitriol in a flask, 
ae a, Fig. 243, the decomposition giving 
equal volumes of carbonic acid and 
carbonic oxide, as is explained under 
oxalic acid. The acid may be sepa- 
rated by passing the mixture through 
a bottle, 6, containing potash water, 
and the oxide collected over water. But the best process 
for procuring it is to heat one part of prussiate of potash 
with ten of oil of vitriol in a retort: the carbonic oxide 
comes over in a state of purity. 
As obtained by any of these processes, it is a colorless 


What are the properties of diamond? What are those of ivory black? 
What are the oxygen compounds of carbon? What is the action of car- 
bon and of metallic iron on carbonic acid at ared heat? How is carbonie 
oxide produced from oxalic acid? From what other substance may it be 
procured ? 


CARBONIC ACID. 241 


gas, which may be kept over water, in Fig. 244, 
which it is only sparingly soluble. It 
is without odor, and is irrespirable. A 
jet of it burns in the air with a beauti- 
ful blue flame, combining with oxygen 
and yielding carbonicacid. Its specific 
gravity is 0°9722: it has never been 
liquefied. It is the combustion of this 
gas which produces the blue flame oft- 
en seen in a coal fire. Carbonic oxide a 

is a compound radical, giving origin to a series of bodies. 


LECTURE LIV. 


Carsonic Acip.—Methods of Preparation by Decomposi- 
tion and Combustion.— General Properties, and Relation 
to Combustion and Respiration.—Its Solution in Water. 

. —EHxists in the Breath.—Its Liquid and Solid Forms. 
—Inght Carbureted Hydrogen—Marsh Gas.—Natu- 
ral and Artificial Production—Olefiant Gas.— Action 
with Chlorine. 


CARBONIC ACID. CO2 = 23-066. 
Carponic acid is commonly prepared by the action of 
dilute hydrochloric acid on chalk, or any carbonate of 
lime, the action being 


CaO, CO,4HC...=...CaCl,HO+CO,; 


that is, one atom of carbonate of lime and Fig. 245. 
one of hydrochloric acid yield one atom of 
chloride of calcium and one of water, and one 
atom of carbonic acid gas is set free. The 
process may be conducted in a flask, as in the 
figure, the gas being evolved so rapidly that 
it may be collected over water, though that == 
liquid absorbs it very freely. Se 

Carbonic acid is abundantly formed in many process- 
es. It is the result of the complete combustion of carbon- 
aceous bodies, is evolved during the respiration of ani- 


What are the properties of this gas? How is carbonic acid gas made? 
Under what circumstances is carbonic acid formed during combustion? In 
what other processes does it appear? 


42 CARBONIC ACID. 


mals, and in alcoholic fermentation. It is the fixed air of 
the older chemists. 

It is a colorless and transparent gas at common tem- 
peratures, with a faint smell and slightly acid taste. It is 
irrespirable, and acts in a diluted state as a narcotic pois- 
on; even air, containing one tenth of its volume of this 

Fig. 246. gas, produces a marked effect. Its specific 
gravity is 1-527, and it may, therefore, be 
collected by displacement (Fig. 246). For 
\\ the same reason, it collects in the bottom of 
) wells and pits, and often suffocates work- 
=_f men who descend into such places. It does 
not support combustion; a lighted taper lowered into a 

Fig. 247, Jar partly filled with, it is extinguished the mo- 
ment it reaches the gas (Fig.247). It may be 
poured from one vessel to another, and if a jar of 
it is poured upon the flame of a candle, the light 
is at once extinguished. Its Capsty: and other 


g ) formed by the action of fuming nitric acid on 

‘ carbonate of ammonia, a smoky cloud marking 
its position and movements. 

Carbonic acid reddens litmus water, but the blue col- 
Fig.248. or is restored on boiling, the acid Fig. 249. 
being driven off by the heat. It is 
soluble in water, which, under in- 
creased pressure, takes up several 
times its volume of it, constituting 
the soda water of the shops. Its 
solubility may be established by 
agitating it with water in Hope’s 
eudiometer, Ig. 248, or by passing it 
through Nooth’s soda-water machine, Pg. 
249. 

A common test for the presence of car- 
bonic acid in wells is to lower a lighted 
candle, and if its flame be extinguished, 
it is inferred that the gas is present; but it does not SE 
low that a man may safely descend into such places though 
a candle will continue to burn. 


What are its properties? What are its relations to combustion? 
What is its specific gravity? What is soda water? How may carbonic 
acid he detected ? 


CARBON AND HYDROGEN. 243 


If, through a tube, the breath be made to pass into 
lime-water, a deposit of carbonate of lime renders the 
water milky; or, if the breath be conducted through lit- 
mus water, the color changes to red; the air thus expired 
from the lungs contains three or four per cent. of carbonic 
acid. 

Under a pressure of thirty-six atmospheres, carbonic acid. 
condenses into a liquid characterized by the extraordinary 
quality that it is four times more expansible by heat than 
even atmospheric air. This liquid, when allowed to es- 
cape through a jet, evaporates so rapidly, and produces so 
much cold, that a portion of it instantly solidifies. Solid 
carbonic acid is a substance not unlike snow; mixed with 
alcohol or ether, it produces a degree of cold equal to 
—180° Fahr. 

Although carbonic acid has the name of an acid, it pos- 
sesses the properties indicated by that term in a feeble 
degree. The gas contains its own volume of oxygen. 
The common test for its presence is lime-water, whicli is 
rendered turbid by it. 


CARBON AND HYDROGEN. 

These substances unite, producing many compounds, 
some of which are solid, some liquid, and others gaseous. 
They are of course all combustible bodies, and the de- 
scription of nearly all of them belongs to organic chem- 
istry. 

LIGHT CARBURETED HYDROGEN, CH, = 8:04, 
occurs abundantly in coal mines, and forms with their 
atmospheric air explosive mixtures; it is also found dur- 
ing the putrefaction of vegetable matter under water ; 
on stirring the mud of ponds, bubbles of this gas escape; 
hence the name marsh gas. It may be obtained artificially 
by heating acetate of potash with hydrate of baryta. 


(KO) + (C,H,0;) + (BaO, HO)...=...(KO, CO,)+ 
; (Ba0, CO,) + 2CHL, | 
that is, one atom of acetate of potash with one of hy- 


drate of baryta yield one of carbonate of potash, one of 
carbonate of baryta, and two of light carbureted hydro- 


How can its existence in the breath be proved?) What are the proper- 
ties of liquid and solid carbonic acid? What is the test for it? How may 
light carbureted hydrogen be made? Where is it found naturally ? 


944 OLEFIANT GAS. 


gen gas, the acetic acid being decomposed, by the aid of 
water, into carbonic acid and marsh gas. It is a color- 
less gas, burns with a yellow flame, producing water and 
carbonic acid. Its specific gravity is 0555, forms explo- 
sive mixtures with air, and is the fire damp of coal mines. 
The choke damp, which exists in mines after an explo- 
sion, is carbonic acid gas, originating from the combustion. 


This gas is decomposed by chlorine in the light, but not 
in darkness. 


OLEFIANT GAS. C,H, = 28°16. 


& 

Olefiant gas may be made by heating one part of alco- 

Fig. 250. hol with four of sulphuric acid in 

a flask, a, Pg. 250. The vapor of 
ether which comes over with it may 
be removed by causing the gas to 
pass through a small bottle, 4, con- 
taining sulphuric acid, before being 
collected at the trough. It may also 
be obtained by an apparatus such as Fug. 251, in which 


yy MIMI i 
Sule ARE 
cS MTA = 


pez 


STUDENT It ee 


ul! maaan 


44a 


SMM MPANTENAN YC CSTR ASO TAL ET 


< 


é is the flask pais alcohol and sulphuric acid, and a 
an interposed globe to receive the ether, oil of wine, and 
water, which distill over. 

Olefiant gas is transparent and colorless ; burns with a 
beautiful flame (Pg. 252, page 245) ; forms an explosive 
mixture with oxygen, giving rise by its combustion to car- 


Of what does the explosive gas of coal mines consist? How is olefiant 
gas prepared? What are the “products of combustion of olefiant gas? _ 


CYANOGEN. 245 


bonic acid and water. If mixed with . Fig. 252. 
an equal volume of chlorine, the gases | 
condense into an oily liquid, from which 

olefiant gas has received its name. With 

twice its volume of chlorine, if it be set a 
on fire, hydrochloric acid is formed, and 
carbon is deposited as a dense black 2=== 


smoke. ——— 
Olefiant gas also exists as one of the © = Se 
chief ingredients in the gas employed > 


for illuminating cities. 


LECTURE LV. 


Cyanocen.— Modes of Preparation.—Liquefaction.—An 
Electro-negative Compound Radical. — Bisulphuret of 
Carbon.—Boron.—Boracic Acid.— Terfluoride of Bo- 
ron.—SiLicon.—Silicic Acid.— Fluoride of Silicon — 
Compounds of Hydrogen and Nitrogen Amidogen.— 
Ammonia.—Ammonium.— Theory of Berzelius. 

CYANOGEN, Cy..OR BICARBURET OF NITROGEN. C,N=26'23. 
CaRBoN unites with nitrogen, forming a bicarburet, 

when these substances are in the nascent state and in pres- 

ence of a base. It may be obtained very easily by expo- 

sing the cyanide of mercury to heat, or by heating a mix- 

ture of six parts of ferrocyanide of potassium and nine of 

corrosive sublimate. 

It is a colorless gas, having a peculiar odor. It burns 
with a beautiful purple flame, dissolves readily in water, 
and still more so in alcohol, condenses into a liquid by a 
pressure of 3°6 atmospheres at 45° Fahrenheit, as may 
be shown by heating with a lamp cyanide of mercury ina 
bent tube, as seen in Fig. 253; the tube Fig. 253. 
being closed at both ends, liquid cyanogen 
accumulates at the cool extremity. Though 
a compound body, it has all the properties 
and characters of a powerful electro-nega- 
tive element. A farther description of it 
and its compounds will be given under organic chemistry. 


What is the action of chlorine on it? From what has it derived its 
name? How is cyanogen made? ran may it be condensed into a liquid ? 


246 SULPHUR AND CARBON. 


BISULPHURET OF CARBON, CS, = 38°28, 
may be made by passing the vapor of sulphur over char- 
coal ignited in a tube, and receiving the product in a cold 
bottle ; the apparatus is represented in Fig. 254. Into 


the top of a large iron bottle two tubes, 8 c, one straight 
and the other bent, are inserted; the bottle having been 
filled with charcoal, pieces of brimstone are dropped in 
through the tube 4, as soon as the bottle is red hot. The 
sulphur and carbon unite. ‘The product passes along the 
tubes c f, cooled by a stream of water from the cock, d, 
the water being conducted by a string, 4, into a basin, 2. 
The vapor passes into the bottle, 2, which is partially filled 
with ice, and the incondensable gases pass out through m. 
It is a transparent liquid of a very disagreeable odor, has 
the quality of dissolving sulphur and phosphorus, boils at 
108° Fahrenheit, and is therefore very volatile. 
BORON, B=10°, 

was discovered by Davy as the basis of boracic acid, from 
which it may be set free by potassium at a red heat. It 
is an olive-colored solid, which burns when ignited in ox- 
ygen gas or atmospheric air, and produces boracic acid. 


BORACIC ACID. BO, = 34°939. 
Boracic acid exists in the waters of the volcanic springs 


of Tuscany. It is also brought from India combined with 
soda, and may be artificially procured by dissolving one 


How is bisulphuret of carbon formed? From what is boron derived? 
How is boracic acid prepared ? 


t 


SILICON. 247 


part of borax in four of hot water, and adding half a part 
of sulphuric acid. On cooling, the boracic acid is depos- 
ited in small crystalline scales, which may be purified by 
recrystallization. 

Boracic acid melts at a red heat Fig. 255. 
into a transparent glass. Its crystals 
raised to 212° Fahrenheit, lose half 
their water. It volatilizes readily 
when boiled in water, is soluble in 
alcohol, the solution burning with a 
green flame. The experiment may 
be made in a glass instrument like Fig. 255,a bc. Itis 
avery feeble acid, and even turns yellow turmeric brown, 
like an alkali. 

TERFLUORIDE OF BORON, BF, = 66°94, 

is formed when a mixture of fluor spar, boracic acid, and 
oil of vitriol is heated in a flask. Jt is decomposed by 
water, by which it is'rapidly absorbed. In damp air it 
forms white fumes. e 


SILICON. Si=22'18. A 

This element may be prepared by igniting the silico- 
fluoride of potassium with potassium, 
acting upon the resulting substance 
with water, which removes the fluor- 
ide of potassium, and leaves the sili- 
con as a nut-brown powder. 

It exhibits two allotropic states. 
Prepared as first described, it takes 
fire and burns when heated in atmos- 
pheric air; but if previously ignited 
in close vessels, it shrinks in volume, 
and, passing into its other state, becomes incombustible in 
oxygen gas. 


SILICIC ACID. S7zO; = 46:219. 

Silicic acid is one of the most abundant bodies in na- 
ture, existing under the innumerable forms of the quartz 
minerals, sands, and sandstones. Rock crystal and flint 
are pure silicic acid. 

It may be obtained in a more convenient form by fusing 


What is the color it communicates to flame? How may silicon be pre- 
ared? In what respect does it differ after ignition? What is the con- 
stitution of silicic acid, and how may it be prepared ? 


248 FLUORIDE OF SILICON. 


white sand with four parts of carbonate of potash, dissolv- 
ing the resulting silicate in water, and decomposing the 
solution with hydrochloric acid. The silicic acid sepa- 
rates as a gelatinous hydrate, slightly soluble in water, 
which, when washed and dried, yields a white powder 
absolutely insoluble in water. ‘There is reason to be- 
lieve that the silicon exists in its different allotropic states 
in these two forms of silicic acid. 

Silica is a gritty substance, sufficiently hard to seratch 
glass. Its specific gravity is 2°66. It combines with the 
alkalies in excess to form glass. It requires a high tem- 
perature for fusion. Hydrofluoric acid is the only acid 
which dissolves it. 


FLUORIDE OF SILICON, S7F; = 78°22, 

may be obtained, as just stated, by dissolving silica in hy- 
Fig. 257. drofluoric acid, or by heating 

7 a mixture of fluor spar and 

sand with sulphuric acid. It 
is colorless ; fumes in the 
air; its specific gravity is 
3°66. Transmitted from the 
flask which generates it, a, 
Fig. 257, through water, it 
is decomposed, hydrated sil- 
ica being deposited. To pre- 
vent the tube which delivers 
the gas being stopped up by 
the silica, some quicksilver, 

e, may be put in the vessel, 
d, and the tube dipped into 
~ it, so that the bubbles of gas_ 

may not come in contact with the water until they have 
reached the surface of the metal ; the sulphuric acid may 
be introduced through the fateh: i. In the water, hydro- 
fluosilicic acid forms, which is sometimes used as a test 

for potash. 
NirroGen and Hyproeen yield three compounds : 


they are designated respectively by the names 


Whatare its properties? When the fluoride of silicon is passed through 
water, what are the products? How many compounds of nitrogen and 
bydrogen are admitted ? 


AMIDOGEN. 249 


Amidogen. 
Ammonia. 
Ammonium. 


AMIDOGEN. NH; = 1619. 

Amidogen is a hypothetical compound radical, the ex- 

istence of which, in several compounds, is inferred. On 

heating potassium in ammoniacal gas, one third of the hy- 

drogen is set free, and an olive substance remains, the 

amidide of potassium. This, in contact with water, yields 
potash and ammonia. 


KK, NE, HO’... = KO NE. 


Amidogen is an electro-negative compound radical like 
cyanogen. 


AMMONIA. NH; = 17°19. 
This substance, called also volatile alkali, from its 
properties, is an abundant product of the putrefaction of 
animal matters, and may be obtained by the destructive 
distillation of horn ; hence the term, spirit of hartshorn : 
it also exists in the air, and is a common product of many 
chemical reactions. 
It may be obtained by heating in a flask, 
a, Fig. 258, equal quantities of slacked 
lime and muriate of ammonia, and, as its 
specific gravity is only 0°590, it may be col- 
lected, as in the cut, in a flask or jar, 3, 
with the mouth downward, by displacing 
the heavier air. The action is, 


(NH; + HCl) + (CaO, HO)...=... 
CaCl + 2HO + NH. 

It is a transparent and colorless gas, of excessive pun- 
_ gency, and having all the qualities of a strong alkali. It 
turns turmeric paper brown, is absorbed with wonderful 
rapidity by water, which, at 32° I’., takes up 780 times 
its volume of the gas, a result which may be illustrated 
by inverting a flask full of it in some cold water, when the 
water rushes up with sufficient violence to destroy the 
flask very frequently. Ammonia neutralizes the strongest 
acids, as may be shown by dropping it into litmus water 
which has been reddened by sulphuric or nitric acid. 


What is amidogen? From what substances may ammonia be pro- 
cured? Whatisitsspecitic gravity? What class of bodies does it closely 
resemble? How may its altinity for water be illustrated? How does it 
act on reddened litmus water? 


250 AMMONIA. 


Fig. 259. It is composed of three volumes of hydro- 
: gen with one of nitrogen, condensed into two 
volumes. It may be recognized by its re- 
markable odor, and by the formation of white 
clouds when a rod, a, Fig. 259, dipped in 
muriatic acid, is approached to it. It con- 
denses into a liquid at 60° under a pressure 
of 6:5 atmospheres. 

Its solution in water, known as aqua ammonie, is pre- 
pared by passing the gas evolved from slacked lime and 
sal ammoniac through Wolfe’s bottles, as 1S represented 
in Fig. 260; the water will take it up until its specific 

3 Fig. 260. 


gravity is lowered to 0°872; it then contains 321 per 
cent. of gas. This solution, somewhat diluted, is much 
used by chemists for neutralizing and precipitating. It 
also affords the best means of obtaining ammonia, mere- 
ly requiring to be warmed in a flask, when the gas read- 
ily comes off. 


AMMONIUM, Am = NH, = 18°19, 
is a hypothetical body, and believed to be of a metallic 
nature ; its symbol is, therefore, Am. It may be combined 
with mercury by decomposing a solution of an ammoni- 
acal salt by a Voltaic current, the negative pole being in 
contact with a globule of that metal, or by putting an 


What is its constitution? How may it be detected? By what pro- 
cess is aqua ammonis made? What is the nature of ammonium? In 
what state may it be obtained ? 


AMMONIUM. 251 


amalgam of potassium and mercury in water of ammonia. 
Under these circumstances, the mercury swells, and event- 
ually becomes of a soft consistency like butter, preserving 
its metallic aspect completely. All attempts to separate 
the ammonium from this amalgam have failed. It decom- 
poses into VM; and H. 

It is now generally agreed by chemists that ammonium 
is the basis of the salts of ammonia. Thus, sal ammoniac, 
called also the muriate of ammonia, is NH, + HCl; but 
this is evidently the same as NH, + C7, that is, the chlo- 
ride of ammonium. In all cases where ammonia forms 
neutral salts with the so-called oxygen acids, it requires an 
atom of water, but this water evidently gives it the con- 
stitution, not of NH, + HO, but NH, + O; the water, 
therefore, makes it oxide of ammonium, which will unite 
with sulphuric, or nitric, or any other acid, precisely after 
the manner of any other metallic oxide. Moreover, the 
compounds of ammonia with this atom of water are iso- 
morphous with the compounds of the oxide of potassium. 
From these facts, therefore, we see that when sulphuric 
acid unites with ammonia, the atom of water which the 
acid contains gives to the salt the constitution 


INNH,, O + SO,, or NH, + SO,, or Am+ SO,, 


the latter formula being analogous to Am + C1, the chlo- 
ride of ammonium or salammoniac. ‘This view of the na- 
ture of the ammonia compounds is known under the name 
of the ammonium theory of Berzelius. 

Of the compounds of ammonium with other bodies, the 
protosulphuret, NH,, S, may be mentioned under the 
name of hydrosulphuret of ammonia. It is much used as 
atest. There are also other sulphurets. 


’ 
1 


How can it be shown that it is the base of the ammonia salts? What 
is meant by the ammonium theory of Berzelius ? 


THE METALS. 


LECTURE LVI. 


GrenersL Properties or THE Metats.— Definition of a 
Metal.—Color, Specific Gravity, Hardness, Tenacity, 
and other Properties.—Relations to Heat.— Compounds 
with other Bodies.—Division into Groups.— The Oxides 
and their Reduction.— The Sulphurets and their Reduc- 
t10n. ‘ 


Or the elementary bodies, by far the larger portion are 
metallic. By a metal we mean a body which possesses 
that peculiar manner of reflecting light which is known 
under the designation of metallic lustre. It is also a good 
conductor of electricity and heat. Of these there are at 
least forty-two, and probably forty-five, three having been 
recently discovered. 

Most of the metals are of a white color, but they differ 
from each other by slight shades, some having a faint blue 
and others a pinkish tint. ‘There are three which are strik- 
ingly Gslored: : gold, which is yellow, and copper and ti- 
tanium, which are red. In specific gravity they differ ex- 
ceedingly ; potassium is so light as to float upon water, 
and iridium is twenty-six times as heavy as that liquid. 

Many of the metals are malleable, that is, can be ex- 
tended into thin sheets under the blows of a hammer; 
others are so brittle that they may be reduced to powder 
in a mortar; some of them are ductile, and may be 
drawn into fine wires, the order for malleability not being 
the same as that for ductility. Thus, iron may be drawn 
into fine wire, but can not be beaten out into such thin 
sheets as many other metals. Of all metals gold is the 
most malleable, and platina has been drawn into the finest 
wires. 


What is the definition of a metal? How many metals are there? 
What is their color commonly’? Which three are the colored metals? 
Of the metals, which is the lightest, the heaviest, the most malleable, the 
softest, the hardest, the most fusible, and the most volatile ? 


PROPERTIES OF THE METALS. 253 © 


In hardness the metals differ much. Potassium is so 
soft that it may be moulded by the fingers, but iridium is 
among the hardest bodies known. In tenacity or strength 
the same differences are seen: of all metals iron is the 
most tenacious. The same metal differs very much in 
this respect at different temperatures. 

In their relations to heat, well-marked distinctions also 
may be traced. Mercury at all ordinary temperatures is 
in a melted condition; but platina can only be fused be- 
fore the oxyhydrogen blow-pipe. As respects volatility, 
mercury, cadmium, potassium, sodium, zinc, arsenic, and 
tellurium, may be distilled or sublimed at a red heat. 

The metals unite with electro-negative bodies, and with 
each other. In decomposition by the Voltaic battery, they 
pass to the negative pole, and are, therefore, described as 
electro-positive bodies. Their compounds with oxygen, 
chlorine, &c., pass under the names of oxides, chlorides, 
&c.; their compounds with each other under the name of 
alloys, or, if mercury be present, of amalgams. They also 
unite with sulphur, phosphorus, and carbon. 

Chemical writers usually divide the metals into groups 
founded upon their relations with oxygen gas. The fol- 
lowing simple division is the one I adopt: Ist. Metals 
which decompose water at common temperatures; 2d. 
Metals which can not decompose water at common tem- 
peratures, but do it at a red heat; 3d. Metals which can- 
not decompose water at all. 


lst Group. Cerium. Titanium. 
Potassium. Manganese. Arsenic. 
Sodium. Tron. Antimony. 
Lithium. Nickel. Tellurium. 
Barium. Cobalt. Uranium. 
Strontium. Zinc. Copper. 
Calcium. Cadmium. Lead. 
Magnesium. Tin. Bismuth. 

Silver. 

Qd Group. 3d Group. Mercury. 
Aluminum. Chromium. Gold. 
Glucinum. Vanadium. Palladium. 
Thorium. Tungsten. Platinum. 
Yttrium. Molybdenum. Rhodium, 
Zirconium. Osmium. Iridium. 
Lanthanum. Columbium. rs 


The older chemists divided the metals into four class- 
es: Ist. Alkaline, such as potassium. 2d. Earthy, such 


With what other substances do they unite? Into what groups may 
they be divided? What is the division formerly in use? 
ia 


254 METALLIC OXIDES. 


as magnesium. 3d. Imperfect, as zinc. 4th. Noble, as 
gold. 


THE METALLIC OXIDES. 

Metallic substances unite with oxygen with different de- 
grees of intensity, and in very different proportions, many 
of them giving rise to a complete sees of oxides, and - 
producing, 1st. Basic oxides. 2d. Neatr@ or indifferent 
oxides. 3d. Metallic acids. 

1st. The basic oxides are commonly protoxides or ses- 
quioxides, which form neutral salts with hydrogen acids, 
with the production of water. ‘To form such salts, for 
every atom of oxygen in the base there is required one 
atom of acid. A basic protoxide, therefore, requires one 
atom of acid, a’sesquioxide three, and a deutoxide two, 
to form a neutral salt. 

2d. The neutral, or indifferent, oxides contain more 
oxygen than the base, and, when heated with acids, give 
off that oxygen, a basic oxide resulting. 

3d. The metallic acids always contain more oxygen ; 
they may be sesquioxides, deutoxides, teroxides, or quadr- 
oxides, and are commonly formed by deflagrating the 
metal with nitrate of potash. 


REDUCTION OF THE METALLIC OXIDES. 

Some of the oxides, such as those of mercury, silver, 
and gold, may be reduced by heat alone ; but the great- 
er number require the conjoint action of carbon, which, 
at a high temperature, decomposes them with evolution of 
carbonic oxide. Among powerful reducing agents may 
be mentioned the formiates and the cyanide of potassium, 
the former acting through the affinity of carbonic oxide 
for oxygen, and the latter through the affinity of carbon 
and potassium conjointly. The deoxydation of metals may 
also be accomplished by reducing agents, such as phos- 
phorous and sulphurous acids, or by the action of other 
metals ; iron, for instance, will precipitate metallic copper 
from its solutions. 

The Voltaic current affords a powerful means of ef- 
fecting the reduction of metals in philosophical investiga- 
tions; by its aid the alkaline metals were originally ob- 
tained. The electrotype, already described, is an exam- 


What substances do metals yield with oxygen? How are metallic acids 
commonly made? By what processes may metallic oxides be reduced ? 


METALLIC SULPIUURETS. 255 


ple of its action; even solutions of metallic salts are 
readily decomposed by it. Thus, if a Fig. 261. 

glass jar, T, Hig. 261, be divided into 
halves, and a paper diaphragm be in- 
weduced between them, the halves being BE = 
tightly pressed together bythering BB, {| 
if the jar be filled with any metallic so- 
lution, suchas the sulphate of soda, and (XO 
the positive and negative wires nis the * ss 
battery dipped in the opposite compartments, after a time 
the metallic oxide will be found in one of them and the 
acid in the other, a total decomposition having taken place. 


THE METALLIC SULPHURETS. 

Many of these, such as the sulphurets of iron, lead, and 
copper, are found abundantly in nature; or they may be 
made artificially by heating the metal with sulphur, or by 
deoxydizing metallic sulphates by charcoal or hydrogen 
gas, which converts them into sulphurets; or by the ac- 
tion of sulphureted hydrogen on their oxides, which yields 
a metallic sulphuret and water. From their solutions 
under these circumstances, iron, manganese, zinc, cobalt, 
and nickel can not be precipitated, though they may by 
hydrosulphuret of ammonia. 

The sulphurets of a metal are usually equal in num- 
ber, and similar in constitution to its oxides; and as ox- 
ygen compounds unite with each other to produce oxygen 
salts, the sulphurets, in like manner, also unite with each 
Other to produce sulphur salts. 


REDUCTION OF THE SULPHURETS. 

The metallic sulphurets may often be reduced by melt- 
ing them with another metal having a more powerful af- 
finity for sulphur; thus, iron filings will decompose sul- 
phuret of antimony, sulphuret of iron forming, and anti- 
mony being set free. On the large scale, however, a 
different process is resorted to; the sulphuret, by roast- 
ing, is converted into a sulphate, much of the sulphur 
being expelled during the process as sulphurous or sul- 
phuric acid. The resulting sulphate is then acted upon 


! 


By what processes may metallic sulphurets be obtained? What metals 
can not be precipitated by sulphureted hydrogen? What relation exists 
between the sulphurets and oxides? How are the sulphurets reduced? 
What is the process on the large scale ? 


256 POTASSIUM. 


by lime and carbon at a high temperature; the lime de- 
composes the sulphate, setting free the metallic oxide, 
which is at once reduced by the carbon, the sulphate of 
lime turning simultaneously into the sulphuret of calci- 
um, which floats on the surface of the metal as a slag. 

The metals also unite with chlorine, iodine, bromine, 
carbon, phosphorus, &c., and some with hydrogen and 
nitrogen. ‘These compounds will be described in their 
proper places. 


LECTURE LVII. 


Porasstum.— Discovery of, and Properties—Relations to 
Oxygen and Water.—Its Oxides.—Caustic Potash.— 
Tests for Potash—Haloid Compounds of Potassium.— 
Salts of the Protoxide, the Carbonate, Nitrate, Chlorate, 


§c. 

POTASSIUM. K =39°15. 

Potassium was first obtained by Sir H. Davy, who de- 
composed its hydrated oxide (potash) by a Voltaic cur- 
rent. From the positive pole oxygen gas escaped in bub- 
bles, and metallic potassium in globules appeared at the 
negative. 

It was subsequently discovered that the same sub- 
stance could be decomposed by iron, and also by carbon 
at a high temperature ; and the latter of these substances 
is now exclusively resorted to for the preparation of po- 
tassium. The carbonate of potash is ignited with char- 
coal in an iron bottle, and the potassium received into a 
vessel containing naphtha. The productiveness of the op- 
eration is greatly interfered with by the circumstance 
that the carbonic oxide which is evolved, as it cools be- 
low a red heat, unites with much of the potassium, pro- 
ducing a gray substance, which chokes the tubes and 
diminishes the yield of the metal. 

Potassium is a bluish white metal, which, at 32° F., is 
brittle, melts at 150° F., and boils at a red heat, yielding 
a green vapor. Its specific gravity is ‘865; it is, there- 


From what was potassium first obtained? What process is now in 
use for its preparation? What circumstance interferes with the produc- 
tiveness of this process? What are the properties of potassium ? 


OXIDES OF POTASSIUM. 257 


fore, much lighter than water, on the surface of which it 
floats. At 70° I’. it may be moulded by the fingers, be- 
ing soft and pasty. 

‘Tt possesses an intense affinity for oxygen, _‘Fig. 262. 
and hence requires to be preserved in bot- 22 
tles containing naphtha. A piece of it thrown ie 
upon water takes fire, and burns with a beau- _— 
tiful pink flame. In the air it speedily tar- 
nishes, and, even when brought in contact 
with ice, itdecomposes it with the evolution of flame. In 
these cases the combustion arises from the hydrogen unit- 
ing with the oxygen of the air and reproducing water ; 
the potassium simultaneously burns. 

POTASSIUM AND OXYGEN. 

There are two oxides of potassium, a protoxide and a 

peroxide, 


HOW HO:: 


The affinity of potassium for oxygen is so great that it takes 
that substance from almost all other bodies, and hence is 
used as a powerful deoxydizing agent. 


Protoxide of Potassium. KO = 47163. 


This substance can only be formed by the action of po- 
tassium on dry air or oxygen. It possesses a great affin- 
ity for water, and is converted by it into the hydrated ox- 
ide of potassium, commonly called caustic potash. 


Hydrated Oxide of Potassium. KO, HO = 56:176. 


This substance is best procured by boiling two parts of 
pure carbonate of potash with twenty of water, and hav- 
ing previously slacked one part of quicklime with hot wa- 
ter, the cream which it forms is to be added by degrees, 
and the whole boiled. The process should be conducted 
in an iron vessel to which a lid can be adapted, so as to 
exclude the air during cooling; the resulting carbonate 
of lime settles perfectly, and the hydrate may be obtained 
by evaporating the solution rapidly in a silver vessel, pour- 
ing out the melted residue on a silver Bia or casting it 
into the form of small cylinders. 

The decomposition which takes place in the foregoing 
process is simple, 

How many oxides does it form? How is the hydrated oxide, or caustic 
potash, obtained? What is the 8 of the decomposition ? 


258 OXIDES OF POTASSIUM. 


KO, CO... + ;Ca0, HO... 21 CaO, CO; + KOA ; 


that is, the lime takes carbonic acid from the carbonate of 
potash, and the oxide of potassium unites with water. The 
solution may be known to be free from carbonic acid by 
not effervescing when mixed with stronger acids. 

The hydrate of potash is a white solid, having a power- 
ful affinity for water, and abstracting it rapidly from the 
air. Taken between the fingers, it communicates to the 
skin a soft feel, and, if a-concentrated solution be used, 
soon effects a disorganization; hence it is used by sur- 
geons in the form of small sticks as an escharotic. It 
possesses pre-eminently the alkaline qualities, and, indeed, 
may be taken as the type of that class of bodies, neutral- 
izes the most powerful acids perfectly, and communicates 
to turmeric paper, or turmeric solution, a brown tint. It 
turns the infusion of red cabbage green, and, possessing 
an intense affinity for carbonic acid, is used in organic 
analysis to absorb that gas. 

Potash in combination occurs in all fertile soils, and is 
essential to the growth of land plants, from the ashes of 
which its carbonate is abundantly procured. This may be 
shown by filtering water through the ashes of wood, when 
the clear liquid will be found to answer to all the tests in- 
dicating the presence of potash. It occurs also abundant- 
ly in feldspar, and hence is found in clays. The want of 
fertility in soils appears occasionally to be due to the ab- 
sence of this body. 

The bichloride of platinum gives, with a solution of 
potash, a yellow precipitate of the chloride of platinum 
and potassium. When the amount of potash is small, it 
is well to add alcohol at first, in. which the double chlo- 
ride is insoluble. Ammonia yields a similar precipitate ; 
but this may be avoided by exposing the substance, in the 
first instance, to a red heat before testing. Perchloric acid, 
with alcohol, yields a white precipitate. Tartaric acid, 
if added in excess, and the mixture stirred with a glass 
rod, bearing gently on the sides of the vessel, gives white 
streaks of the bitartrate of potash wherever the rod has 
passed over the glass. 


Of what properties is the hydrate of potash possessed, and what are its 
uses? How may the existence of potash in the ashes of plants be proved? 
What are the tests for the presence of this substance ? 


COMPOUNDS OF POTASSIUM. 259 


Of other compounds of potassium, the following may be 


mentioned : é 
Peroxide of potassium, K O3. Bromide of potassium, K Br. 
Chloride of potassium, K Cl. Protosulphuret of potassium, A'S. 
Iodide of potassium, KJ. Pentasulphuret of potassium, K S35. 


It also combines with hydrogen in two proportions, pro- 
ducing a solid and a gas, the latter of which takes fire 
spontaneously in the air. 

Of these compounds, the most important are the per- 
oxide of potassium, which is formed by passing oxygen 
over red-hot potash; it is decomposed by water, evolving 
oxygen and producing potash; the chloride of potassium, 
which is analogous to common salt; the iodide, much of 
which is consumed in medicine, under the name of hy- 
driodate of potash. It may be prepared by dissolving 
iodine in a solution of potash, till the liquid begins to ap- 
pear brown, then evaporating to dryness, and igniting the 
residue: oxygen is evolved, and iodide of potassium re- 
mains; it may be then dissolved in water, and crystal- 
lized. It is white, crystallizes in cubes, and is very sol- 
uble in water and hot alcohol. Its solution will dissolve 
large quantities of iodine. ‘The pentasulphuret is the chief 
ingredient of liver of sulphur, which is formed by fusing 
sulphur with carbonate of potash at a low temperature. 


SALTS OF THE PROTOXIDE OF POTASSIUM. 

Carbonate of Potash is obtained by lixiviating the ashes 
of plants. In an impure state it forms the potashes and 
pearlashes of commerce. It may be obtained pure by ig- 
niting the bitartrate with half its weight of the nitrate of 
potash. It has an alkaline taste, its solution feels greasy 
to the fingers, it is very soluble in water, and deliquescent. 

‘ Bicarbonate of Potash, formed by transmitting a stream 
of carbonic acid through a solution of the former salt. It 
crystallizes in eight-sided prisms with dihedral summits. 

Sulphate of Potash, formed by neutralizing the follow- 
ing salt. Crystallizes in anhydrous, oblique, four-sided 
prisms, soluble in about ten times its weight of water. 

Sulphate of Potash and Water, sometimes designated 
as the bisulphate of potash ; it is the residue of the produc- 
tion of nitric acid. It is soluble in water, and has an acid 
reaction. It crystallizes in rhombohedrons. 


Name some of its other compounds. What are the properties of the 
iodide? From what is the carbonate obtained ? 


260 SALTS OF POTASH. 


Nitrate of Potash is extracted on the large scale from 
certain soils in which organic matter is decaying in con- 
tact with potash. It crystallizes in six-sided prisms, fuses 
at a heat beneath redness, with evolution of oxygen gas. 
It is soluble in about three times its weight of water, at 
common temperatures. This salt enters as an essential 
ingredient in gunpowder, which is composed of.about one 
atom of nitrate of potash, one of sulphur, and three of 
carbon. ‘The sulphur of this mixture accelerates the com- 
bustion, while the oxygen of the nitre forms carbonic acid 
with the charcoal. ‘The products, therefore, of the per- 
fect combustion of gunpowder are carbonic acid, nitrogen, 
and the sulphuret of potassium. It commonly happens, 
however, that sulphate of potash is formed. The pro- 
portions of the ingredients of gunpowder are varied for 
different uses. The powder used for mining, for exam- 
ple, contains more sulphur than that used for firearms. 

Chlorate of Potash—When a stream of chlorine is 
passed into a solution of potash, the chloride of potassium 
and the chlorate of potash result; the latter is deposited 
in flat, scaly crystals. 

The chlorate of potash contains no water; it dissolves 
in about fifteen times its weight of that fluid; melts at a 
red heat, with evolution of pure oxygen; deflagrates with 
combustible bodies, sometimes with much violence. 


LECTURE LVIII. 


Sopium.—Preparation of —Relation to Oxygen and Wa- 
ter —Color communicated to Flame.—LIts Oxides.— The 
Hydrated Oxide— Tests for Sodium— Haloid Com- 
pounds.—Common Salt.-—Salts of the Protoxides, Car- 
bonates, Sulphates, Nitrates, §c. Lirarom.—Barivum. 
—Its Oxides.—Haloid Compounds.—Salts of the Pro- 
toxide. 

SODIUM. Na = 23:3. 
Sop1um may be obtained by the same process as potas- 
sium, but is best procured by igniting the calcined acetate 
of soda with powdered charcoal in an iron bottle; and, as 


pray nha! AS YS ROUSE 
What is the origin and use of the nitrate? How is the chlorate made? 
How is sodium obtained, and what are its uses? 


OXIDES OF SODIUM. 261 


the sodium does not act upon carbonic oxide, the opera- 
tion is much more productive than in the case of the oth- 
er metal. Like potassium, it is to be kept in bottles un- 
der the surface of naphtha. ° 

In color, sodium resembles silver ; its specific gravity is 
0:9348; it therefore floats upon water. It melts at 194° 
F.. and is more volatile than potassium. Thrown upon 
water, it decomposes it with a hissing sound, and with the 
evolution of hydrogen, but no flame appears. If, howev- 
er, the water is hot, then a beautiful yellow flame, char- 
acteristic of sodium and its compounds, is the result. 


SODIUM AND OXYGEN. 
With oxygen sodium forms three compounds : the sub- 
oxide, protoxide, and peroxide. 


Protoxide of Sodium. NaO = 31:313. 


This, like the corresponding potassium compound, is 
produced by oxydizing sodium in dry air. It is a white 
powder, which attracts moisture from the air and forms the 
hydrated oxide of sodium, commonly called caustic soda. 


Hydrated Oxide of Sodium, NaO + HO = 40°323, 


or caustic soda, may be made by the same process as that 
given for caustic potash, by using carbonate of soda, and, 
when the resulting carbonate of lime has settled, evapo- 
rating the liquid. ‘The best proportions are one part of 
quicklime to five of carbonate of soda in crystals. 
Caustic soda resembles caustic potash in most of its 
properties. It is deliquescent, has a strong affinity for 
arbonic acid, and acts upon animal tissues as an escha- 
Botic. Its salts are generally more soluble than the pot- 
ash salts, and on this are founded the methods recom- 
mended for distinguishing the latter compounds from it. 
Moreover, the soda compounds communicate to the flame 
of alcohol, or to the blow-pipe flame, a yellow color: the 
same tint which is characteristically seen when sodium 
is placed in hot water. 


Chloride of Sodium. NaCl = 58°77. 


The chloride of sodium, common salt, is obtained abund- 
antly from the waters of the sea, to which it gives their 


What are its properties compared with potassium? What compounds 
with oxygen does it give? How is caustic soda obtained? What are its 
properties anduses? What color do the sodium compounds give to flame ? 


262 CHLORIDE OF SODIUM. 


salinity. It is also found as rock salt, deposited exten- 
sively in certain geological formations. 

Common salt is the general type of that extensive class 
of compounds which have derived the name of salt bodies 
from it. It crystallizes in cubes, and, when in mass, is 
often perfectly transparent, and permits the passage of 
heat of every temperature through it freely. It melts into 
a liquid at a red heat, crystallizes in cubes, and is not 
more soluble in hot than cold water. It is extensively 
used in the preparation of hydrochloric acid and chlo- 
rine; immense quantities, also, are annually consumed in 
the preparation of carbonate of soda, which is made by 
first acting on the common salt with oil of vitriol, so as to 
turn it into sulphate of soda, and igniting this with char- 
coal and carbonate of lime: an impure carbonate of soda 
is the result, known under the name of black ash, or Brit- 
ish barilla. Common salt is extensively used for the 
curing of meat. It is also an essential article of food, 
being decomposed in the animal system, and furnishing 
hydrochloric acid to the gastric juice and soda to the bile. 

The compounds of sodium with bromine, iodine, sul- 
phur, &c., are not of interest. 


SALTS OF THE PROTOXIDE OF SODIUM. 

Carbonate of Soda is sometimes obtained by lixiviating 
the ashes of sea-weeds. Large quantities are also pro- 
cured from the decomposition of sulphate of soda by saw- 
dust and lime at a high temperature, the carbonaceous 
matter decomposing the sulphuric acid and generating 
carbonic acid, which unites with the soda, while the liber- 
ated sulphur is partly dissipated and partly unites with 
the calcium. From the resulting mass carbonate of soda 
is obtained by lixiviation. The crystals, as found in com- 
merce, contain generally ten atoms of water; there are: 
two other varieties, the one containing eight atoms, and 
the other one atom of water. Large quantities of the 
carbonate of soda are also sold in an uncrystallized state, 
under the name of salts of soda. The figure of the crys- 
tals of this salt is a rhombic octahedron. They effloresce 
on exposure to the air. They are soluble in five times 


What is the constitution of common salt? From what sources is it de- 
rived? What are its properties? How is barilla obtained from it? 
Why is it essential as an article of food? From what source is the car- 
bonate of sodaobtained? Describe the preparation of it from the sulphate. 


SALTS OF SODA. 2638 


their weight of cold and in less than their own weight of 
boiling water. 

Bicarbonate of Soda, or the double carbonate of soda 
and water, is formed by transmitting a stream of carbonic 
acid through a solution of the carbonate, and is in. the 
form of a white powder. It is less soluble in water than 
the former. There is a sesquicarbonate, which passes in 
commerce under the name of trona. 

Sulphate of Soda is the Glauber’s salt of the shops; oc- 
curs as a natural product, and also as the result of the 
preparation of hydrochloric acid. It is in prismatic crys- 
tals of a bitter taste, efflorescing in the air, and becoming 
anhydrous. Water dissolves more than half its weight 
of this salt at 911° F., but above that degree it is less sol- 
uble. When a solution of three parts of this salt in two 
parts of water is corked up in a flask while boiling, it may 
be cooled without crystallization taking place ; but if the 
cork is withdrawn, crystallization commences at once, or 
if it does not, the introduction of any solid matter produ- 
ces it, and the temperature of the solution at once rises. 

Mtrate of Soda is found abundantly in different parts 
of America in the soil; it crystallizes in rhomboids, dis- 
solves in twice its weight of cold water, and, from its del- 
iquescence, can not be used in the manufacture of gun- 
powder. 

Phosphate of Soda (tribasic) is formed by neutralizing 
phosphoric acid with carbonate of soda; two of the hy- 
drogen atoms are replaced; it crystallizes in oblique 
rhombic prisms, dissolves in three times its weight of cold 
® water, is of an alkaline taste, and gives a lemon-yellow 
precipitate with nitrate of silver. By the addition of soda 
to it a subphosphate is formed, in which all three of the 
hydrogen atoms of the acid are replaced; but by the ad- 
dition of phosphoric acid to the ordinary phosphate, till it 
ceases to give any precipitate with chloride of bariam, the 
biphosphate of soda results, a salt very soluble in water. 
Its crystals are rhombic prisms. In it only one of the hy- 
drogen atoms is replaced. 

Microcosmic Salt, or the phosphate of soda, ammonia, 


What is the commercial name of the sulphate? What peculiarity is 
there in the crystallization of its solution? Why can not the nitrate be 
used for gunpowder? What is the difference between the phosphate, 
the pyrophosphate, and the metaphosphate of soda ? 

S 


264 LITHIUM. 


and water, is made by dissolving seven parts of phosphate — 


of soda in two parts of water, and adding one part of sal ain- 
moniac. At a low heat it parts with its water of crystal- 
lization, and the temperature rising, it loses its ammonia 
and saline water, becoming monobasic phosphate of soda. 
It is much used in blow-pipe experiments. 

Pyrophosphate of Soda (bibasic) is procured by heating 
the phosphate. It gives a white precipitate with nitrate 
of silver. 

Metaphosphate of Soda (monobasic) is formed by heat- 
ing microcosmic salt to redness. It is soluble in water, 
melts at a red heat, and gives, with dilute solutions of the 
earthy and metallic salts, viscid precipitates. 

Biborate of Soda, the borax of the shops. It is import- 
ed in a crude state from the East Indies, and manufac- 
tured from the natural boracic acid of Italy by the addi- 
tion of carbonate of soda. It crystallizes in octahedrons, 
or in oblique prisms, the former containing five, the latter 
ten atoms of water, all of which is lost by exposure to a 
red heat, the salt then fusing into a glass. It is of great 
use in blow-pipe experiments. 

LITHIUM. L=6-42. 

This rare metal occurs in certain minerals, such as 
spodumene, lepidolite, &c. It is a white metal, commu- 
nicating to flame a red color. It yields a protoxide the 
carbonate of which is of sparing solubility in water; thus 
forming the link of connection between the potash and 
soda carbonates, which are very soluble, and the carbon- 
ates of the alkaline earths, as baryta and strontia, whic 
are insoluble. 

This brings us to the metals of the alkaline earths, which 
form a division of our first group; the first of these is 


BARIUM. Ba=687. 

The existence of barium was first proved by Davy, who 
isolated it by electrifying mercury in contact with the hy- 
drate of baryta, an amaleam formed, from which the mer- 
cury was subsequently distilled, leaving the barium as a 
metal of a gray color like cast iron, heavier than sulphuric 
acid, in which it sinks, obtaining oxygen rapidly from the 

What is microcosmic salt? From what source is borax derived, and 
what are its uses? In what minerals does lithium occur? What is the 


relation of its carbonate to those of the preceding and subsequent metals ? 
How was barium first obtained ? 


OXIDES OF BARIUM. 265 


air, and giving rise to the production of the protoxide of 
barium, baryta. 


Protoxide of Barium, BaO = 76°713, 


may be obtained by igniting the nitrate of baryta, the de- 
composition being. 

BaO, NOs... =... BaO ++ NO, + O} 
that is, one atom of nitrate of barytes yields one of pro- 
toxide of barium, and one of nitrous acid and one of oxy- 
gen gas are expelled. 

This protoxide is a white colored body, possessing a 
strong affinity for water, with which it exhibits the phe- 
nomenon of slacking, as is the case to a less extent with 
lime, heat being evolved. It has an acrid taste, is soluble 
in water, and absorbs carbonic acid from the air. Its 
ific ; ‘about 4:000. Its soluble salts are pois- 


ate of Baryta, BaO, HO = 85°726, 

is formed by slacking the protoxide, and is a white pow- 
der, very soluble in hot, but less so in cold water, yield- 
ing, therefore, crystals when a hot solution cools: these 
contain nine atoms of water of crystallization. The cold 
solution is used as a test for carbonic and sulphuric acids, 
with which it forms insoluble white precipitates. 

This solution is most easily obtained by calcining the 
native sulphate with pulverized charcoal, which converts 
it into the sulphuret of barium. To a boiling solution of 
this body oxide of copper is added till the liquid ceases to 

lacken a solution of acetate of lead. On being filtered, 
the solution of hydrate of barytes is obtained. 


Peroxide of Barium, BaO, = 84°7, 


is made by igniting chlorate of potash with barytes, or by 
passing oxygen over barytes in ared-hot tube. It is used 
in the preparation of peroxide of hydrogen. 

Of the other compounds of barium, the chloride is much 
used as a test for sulphuric acid; it may be made by de- 
composing carbonate of baryta by hydrochloric acid. The 
sulphuret of barium is made by igniting the sulphate of 


~ What is the process for obtaining the protoxide, and also its hydrate? 
What acids is a solution of baryta used to detect? How is the peroxide 
made? What is its use? For what purpose is the chloride of barium 
employed ? 

Z 


266 STRONTIUM. 


baryta, heavy spar, with charcoal, which deoxydizes both 
the sulphuric acid and the baryta. It dissolves in hot wa- 
ter, and from this solution a solution of caustic baryta 
may be obtained by boiling with the oxides of lead or 
copper, and separating the sulphurets of those metals by 
filtration. By acting upon it with hydrochloric or nitric 
acid, the chloride or nitrate of baryta may be prepared. 


SALTS OF PROTOXIDE OF BARIUM. 

Carbonate of Baryta is found native, as the mineral 
Witherite, and may be prepared by precipitating a solu- 
ble salt of baryta with an alkaline carbonate. It is solu- 
ble in 4300 times its weight of cold water, and 2300 of 
boiling water. 

Sulphate of Baryta, found native abundantly as heavy 
spar, and from it most of the compounds of barium are 
prepared. It is called heavy spar, its density being 4:47. 
It crystallizes generally in tabular Plates aude wholly 
insoluble in water. ne 


LECTURE LIX. 


Strontium.— Uses in Pyrotechny.—Salts of Protowide— 
Catcium.—Protoxide of——Sources in Nature.— Tests 
for.—Haloid Compounds, Chloride, Fluoride, Sulphur- 
ets, &c.—Salts of the Protoxide, Carbonate, Sulphate, 
Phosphate, Chloride—Maenesium.—Protoxide.—Salts 
of Protoxide, Carbonate, Sulphate, Double Phosphate. 
—Atuminum.—Sesquioxide.— Uses in the Arts.— Test 
—Salts of the Sesquoxide, Double Sulphate, Alum— 
Manufacture of Porcelain and Glass.—Other Metals. 


STRONTIUM. Sr= 43:8. 

Tis metal may be obtained by the same processes 
which have been used for obtaining barium, with which | 
it has a considerable analogy. Its natural compounds are 
the sulphate and carbonate, from which its other prepara- 
tions may be obtained. 

Strontium yields a protoxide, which is’ the basis of a 
series of salts, differing from baryta salts in not being 


How m _ How may the sulphate of barytes be converted into the sulphuret of 
barium ? hat are the properties of the carbonate and sulphate of ba- 
ryta? In what respect does strontium differ from barium ? 


CALCIUM. 267 


poisonous. The chloride and nitrate are used in pyro- 
techny for the purpose of communicating to flame a brill- 
iant crimson color. The red fire of theatres contains the 
latter salt, and the former, if dissolved in alcohol, com- 
municates to its flame the characteristic test of the stron- 
tium compounds. 
SALTS OF THE PROTOXIDE OF STRONTIUM. 
Carbonate of Strontia is the strontianite of mineralogists. 
Sulphate of Strontia is the celestine of mineralogists. 
It is not so heavy as sulphate of baryta, and is said to be 
soluble in about 4000 times its weight of boiling water. 

Mitrate of Strontia forms an ingredient of the red fire 
used in theatres; it crystallizes in octahedrons, and is 
soluble in five times its weight of cold water and half its 
weight of boiling water. 


_ CALCIUM. Ca=205. 

Caucium has neverbeen obtained in quantities sufficient 
to permit a full examination of its properties. It oxydi- 
zes with rapidity, yielding a protoxide, known also as 
quicklime or lime. 

Lime occurs as a carbonate in the various limestones, 
marbles, chalks, &c., which form in many countries ex- 
tensive mountain ranges. Its other salts are very abund- 
ant. 

From the carbonate, pure or quicklime may be ob- 
tained by exposure to a bright red heat. If the limestone 
contains silica, it may, however, be overburnt, a silicate 
of lime forming, which prevents the product from slacking. 
It possesses a strong affinity for water, and unites there- 
with with a great elevation of temperature, as exhibited 
in the process of slacking. Exposed to a high tempera- 
ture, it phosphoresces splendidly. The hydrate which 
forms when lime is slacked is white; itis soluble to a small 
extent in water; and it is remarkable that cold water 
dissolves much more than hot. Lime-water is colorless, 
of a partially caustic taste, neutralizes acids perfectly, re- 
storing to reddened litmus its blue color. It is used as a 
test for carbonic acid, with which it gives the white car- 


What is the color it communicates to flame? What are the mineralog- 
ical names of the carbonate and sulphate of strontia? What is lime ? 
Under what forms does it occur in nature? From the carbonate, how may 
lime be produced? What is the action of water on it? What are the 
properties of lime-water ? 


268 COMPOUNDS OF CALCIUM. 


bonate of lime. Cream of lime is nothing but lime-water 
in which hydrate of lime is mechanically suspended. The 
hardening of lime mortars depends chiefly on the absorp- 
tion of carbonic acid. Hydraulic lime possesses the qual- 
ity of setting under water. It contains oxide of iron, 
alumina, and silica. 

Lime is best detected by oxalate of ammonia, with 
which it gives a white precipitate of oxalate of lime, pro- 
vided the solution be not acid. 

Among other compounds of calcium may be mentioned 


Chloride of Calcium, CaCl=55'97, 
formed by dissolving carbonate of lime in hydrochloric 
acid, evaporating the solution to a sirup, and, on cooling, 
the chloride crystallizes. It is exceedingly deliquescent. 
Chloride of calcium, dried without crystallization, is used 
in organic analysis for collecting water, and, generally, in 
other chemical operations for drying gases. 


Fluoride of Calcium, Ca F=39°24, 
called, also, fluor spar, and frequently found as a mineral 
associated with lead. Crystallizes in cubes, octahedrons, 
&c., of various colors. It is found in fossil, and, to a 
smaller extent, in recent bones. It is used for various or- 
namental purposes, and is the source from which the com- 
pounds of fluorine are derived. 


Sulphuret of Calcium, CaS =36°62. 


obtained by igniting the sulphate of lime with charcoal, 
and constitutes Canton’s phosphorus, commonly made by 
igniting oyster shells with sulphur ; possesses the curious 
quality of shining in the dark, after a brief exposure to 
the sun or to the rays of an electric spark. 


SALTS OF THE PROTOXIDE OF CALCIUM. 
Carbonate of Lime is abundantly found in nature, form- 
ing whole ranges of mountains, the limestones, marbles, 
&c., of mineralogists. It occurs pure in the form of Ice- 
land spar, in rhomboidal crystals, possessed of double re- 
fraction. It is dimorphous, assuming the form of six-sid- 
ed prisms, as in the mineral called Arragonite. It is an- 


What is milk of lime? For what purposes is the chloride of calcium 
used? Under what forms does fluoride of calcium occur? What singu- 
lar quality does the sulphuret of calcium possess? What are the dimor- 
phous forms of carbonate of lime ? . 


MAGNESIUM. 269 


hydrous, insoluble in water, but in water charged with 
carbonic acid it is soluble, and is deposited from such a 
liquid on boiling, or by the diffusion of carbonic acid into 
the air. The carbonic acid is expelled from this salt by 
a red heat, and the action of the more powerful acids, 
Carbonate ‘of lime may be obtained in union with water, 
by boiling hydrate of lime with a solution of sugar. 

Sulphate of Lime—Gypsum—occurs native, both in 
crystals, the primary form being a rhombic prism, and also 
in extensive crystalline masses. It contains two atoms of 
water ; there is a variety, however, passing under the name 
of anhydrite, which contains no water. On calcining the 
hydrous sulphate of lime at a low red heat, it becomes plas- 
ter of Paris, and has the property of setting into a hard 
mass when made into a paste with water. The sulphate 
of lime is soluble in 500 parts of boiling water, and often 
occurs in the water of springs, to which it communicates 
hardness. 

Phosphate of Lime—Bone-earth Phosphate—is one of 
the tribasic phosphates ; it is precipitated when earth of 
bones is dissolved in muriatic acid, and the solution neu- 
tralized by ammonia. 

Chloride of jist alah tees Powder—is made by ex- 
posing hydrate of lime to chlorine. It is a white pow- 
der, exhaling a faint odor of chlorine, and is used exten- 
sively as a bleaching agent. 

MAGNESIUM. Mg = 127. 

Maenesium may be procured by igniting a mixture of 
chloride of magnesium and sodium in a porcelain cruci- 
ble ; the chloride of sodium forms, and magnesium is set 
free. The chloride may be dissolved by water. 

It is a white, malleable metal, which melts at a red 
heat, and, with excess of air, oxydizes, forming 


Protowide of Magnesium. Mg O=20°7138. 


This substance, called, also, calcined magnesia, or sim- 
ply magnesia, may be made by heating the carbonate to 
low redness; the carbonic acid is driven off, and the mag- 
nesia remains as a white powder, insoluble in water, but 

Under what circumstances is it soluble in water? Under what forms 
does sulphate of lime occur, and for what purposes is it used? In what 
does the phosphate of lime occur? What is bleaching powder? How is 


magnesiumobtained? What are the properties of it ? Under what names 
does the protoxide pass ? y 
2 


270 SALTS OF MAGNESIUM. 


neutralizing acids completely, and forming with them a 
complete series of salts. 

Magnesia occurs very abundantly in nature, often asso- 
ciated as a carbonate with carbonate of lime, as in dolo- 
mitic limestone. It also occurs in fertile soils, and is es- 
sential to the growth of certain plants. 

It is well distinguished from all the foregoing alkaline 
earths by the relation of its sulphate. The sulphates of 
baryta, strontia, and lime form a series of salts, the solu- 
bility of which, in water, is constantly increasing; to 
these the corresponding magnesia salt may be added ; it 
is very soluble. 

Magnesia is precipitated from its sulphate by the caus- 
tic alkalies, and by the carbonates of potash and soda as 
a carbonate, but not by the carbonate of ammonia in the 
cold. It may be detected by adding carbonate of ammo- 
nia and phosphate of soda in succession, when the phos- 
phate of magnesia and ammonia is precipitated. Heated 
before the blow-pipe, after having been moistened with 
nitrate of cobalt, magnesia becomes of a pinkish color. 

SALTS OF THE PROTOXIDE OF MAGNESIUM. 

Carbonate of Magnesia is found native, and may be 
prepared by boiling the sulphate with an alkaline carbon- 
ate, diffusing the precipitate in water, and passing a 
stream of carbonic acid through it; by spontaneous evap- 
oration the carbonate of magnesia is deposited in crystals. 
The carbonate of magnesia, the magnesia alba of the 
shops, is prepared by precipitating the sulphate of mag- 
nesia with the carbonate of potash; it occurs in light 
white cubical cakes, or in powder, and is not a true car- 
bonate, for it does not contain a full equivalent of carbonic 
acid. It is said to be a compound of one atom of hydrate 
of magnesia with three atoms of hydrated carbonate of 
magnesia. It is very slightly soluble in water. 

Sulphate of Magnesia—Epsom Salts of commerce—is 
produced by the action of dilute sulphuric acid on magne- 
sian limestone. Its crystals are small four-sided prisms, 
soluble in an equal weight of cold and three fourths their 
weight of boiling water, the solution having a bitter taste. 
A low heat expels six out of the seven equivalents of the 
combined water. 


What is dolomitic limestone? How may magnesia be detected? How 
is its carbonate prepared? Of what is Epsom salt composed 3 


ALUMINUM. 271 


Phosphate of Magnesia and Ammonia, one of the vari- 
eties of urinary calculus, may be formed artificially when 
a tribasic phosphate, a salt of ammonia, and a salt of mag- 
nesia are mixed together. 

Magnesium is the last of the alkaline earthy metals. Its 
history completes that of our first group of metallic bodies. 
At the head of the second group we find aluminum, the - 
first of the earthy metals. 


ALUMINUM. Al=13°7. 

Obtained, by Wholer, by the action of sodium on the 
chloride of aluminum, being the same process as that 
given for the preceding metal. 

It is a gray powder, which melts beneath a red heat ; 
takes fire when heated in air, producing 


Sesquioxide of Aluminum. Al,O;=51°539. 


This oxide, called, also, alumina and clay, occurs nat- 
urally under certain forms, which are highly prized, as the 
ruby and sapphire. In a more impure condition it yields 
the various common clays, which also contain silica or 
metallic oxides, or other extraneous bodies. 

Alumina may be prepared from the sulphate of alumina 
and potassa, common alum, by precipitating the sulphuric 
acid by chloride of barium. The sulphate of baryta goes 
down, and there is left in the solution chloride of po- 
tassium and chloride of aluminum. When the mass is 
dried, water is decomposed ; hydrochloric acid is then ex- 
pelled, and alumina, mixed with the chloride of potassium, 
remains behind; the latter is to be dissolved away by wa- 
ter, leaving the alumina as a white substance, which, with 
water, forms a plastic mass, capable of being moulded, 
and retaining its shape when baked. After ignition, it 
adheres to the tongue, and during the act of drying it con- 
tracts considerably in volume, a property which formerly 
gave rise to the invention of Wedgewood’s pyrometer. 

The presence of alumina gives to the clays those prop- 
- erties which fit them for the purpose of the potter and 
brickmaker. Aluminais also used as a mordant to fix the 
colors of certain dyes upon cloth. 


In what form is the phosphate of magnesia and ammonia sometimes 
found? How is aluminum prepared? What is the constitution of its ox- 
ide? Under what natural forms does it occur? How may alumina be 

repared? What principle is involved in Wedgewood’s pyrometer? 
hat is meant by a mordant ? 


272 PORCELAIN.—EARTHEN-WARE.—GLASS. 


Alumina is precipitated from its solutions by fixed al- 
kalies, which yield a white hydrate of alumina, soluble in 
an excess of the precipitant. It is also thrown down by 
alkaline carbonates; and, when these precipitations are 
made in a solution tinged with coloring matter, the alu- 
mina carries it down with it. Such colored precipitates 
pass under the name of lakes; and it is this property of 
attaching such colors to itself, enabling it to cause their 
firm adhesion to cloth fibre, which is the principle of its 
application as a mordant. 

Among the purposes to which alumina is applied may 
be mentioned the manufacture of PorcELam, and the dif- 
ferent kinds of earthen-ware. ‘The former substance, first 
made by the Chinese, is very compact and translucent. 
It consists essentially of clay mixed with a fusible body, 
which binds all its parts together, and is covered with a 
glaze, which does not terminate abruptly on the surface, 
but pervades the substance of the mass. In this respect 
it differs from common earthen-ware. Feldspar, or the 
silicate of lime, are bodies suitable for communicating this 
glassy structure. 

In the manufacture of porcelain, great care is taken to 
select clay free from iron. It is mixed with powdered 
quartz and feldspar, and the requisite shape given it either 
by the potter’s wheel, or by pressing it into moulds. It 
is then dried in the air, and more perfectly in a furnace, 
and, when ignited, forms discuit. ‘This is dipped in the 
glaze, suspended in water, and becomes covered over with 
a uniform coat of it. It now remains to dry it once more, 
and fuse the glaze upon it. 

E:ARTHEN-WARE consists of a white clay mixed with sil- 
ica. It is glazed with a fusible material containing oxide 
of lead, and colored of different tints by metallic oxides ; 
for example, blue by cobalt. 

Connected with the manufacture of pottery, may also 
be mentioned the manufacture of Guass, of which there 
are several varieties, some consisting of silica, potash or 
soda, and lime, others containing a large quantity of oxide’ 
of lead. If silica be heated with carbonate of potash and 
lime, or oxide of lead, carbonic acid is expelled, and glass 


et 


How may the presence of alumina be recognized? What are lakes? 
What substances are used in the preparation of porcelain and earthen: 
ware? How is glass made? 


SALTS OF ALUMINUM. OTs 


forms. The mass is kept in a fused condition till it is free 
from air bubbles, and is then cooled until it becomes plas- 
tic, so that it may be blown or moulded. 

Articles of glass, after they are manufactured, require 
to be annealed or slowly cooled down. This allows their 
parts to assume a regular structure, and ‘prevents excess- 
ive brittleness. 

Soluble glass is formed when silica is heated with twice 
its weight of carbonate of soda or potash. It derives its 
name from the fact that it is for the most part soluble in 
water. 

SALTS OF THE SESQUIOXIDE OF ALUMINUM. 

Sulphate of Alumina is made by dissolving alumina in 
dilute sulphuric acid. It enters ito the composition of 
the alums. 

Sulphate of Alumina and Potash—Alum.—This import- 
ant salt is prepared from alum slate. It crystallizes in 
octahedrons, has an astringent taste, reddens litmus paper. 
It dissolves in about eighteen times its weight of cold, and 
less than its own weight of boiling water. It contains 
twenty-four atoms of water, and, when exposed to heat, 
foams up, melting in its own water, which, being evapo- 
rated away, leaves a white porous mass, commonly called 
burnt alum. 

In the same way that the sulphate of potash unites with 
the sulphate of alumina, so, also, do the sulphates of am- 
monia and of soda, forming respectively the ammoniacal 
and soda alums. ‘The alumina in the common alum may 
be replaced, also, by the sesquioxides of iron, manganese, 
or chromium, giving iron, manganese, and chrome alums. 

The following metals, Guucinum, THorium, YTTRIvuM, 
ZIRCONIUM, LANTHANIUM, and Cerium, are very rare bod- 
ies, and, being of little interest, may be passed over with- 
out farther notice. 


Why must it be annealed? What are the properties of the sulphate 
of alumina and potash? 


274 MANGANESE. 


LECTURE LX. 


Maneanese.—lIts Seven Oxides —The Peroxide and its 
Applications.— Mineral Chameleon. Acids of Manga- 
nese.—Salts of the Protoxide.—Iron.—TIts Natural 
Forms.— Reduction on the Great Scale—Cast Iron.— 
Wrought Iron —Steel.— Passive Iron. 

MANGANESE. Mn= 27°7. 
MancanesE may be procured by igniting its oxides with 

a mixture of lampblack and oil ina powerful furnace, the 

reduction being somewhat difficult. It is a white vimeeie 

specific gravity 8°013, requiring a white heat for its faciou 
and oxydizing readily in the air. It is remarkable for the 
number of oxygen compounds which it yields; they are 
MnO SeviVin,O;...e nO; «Aen Oy soi 
Mn,O,...Mn,0O,, 


designated respectively, 


Protoxide of manganese. Permanganic acid. 
Sesquioxide of manganese. Red oxide of manganese. 
Peroxide of manganese. Varvicite. 


Manganic acid. 

Of these, the protoxide may be made by passing hydro- 
gen gas over red-hot peroxide of manganese. It is of a 
green color, is a basic body, and forms a series of salts, of 
ich the sulphate is used in dyeing. It is isomorphous 
with magnesia and zinc. Hydrosulphuret of ammonia 
yields with it a flesh-colored precipitate, ferrocyanide of 
potassium a white, and the chloride of soda a dark brown 
hydrated peroxide. The sesquioxide is made by igniting 
the peroxide, as will be presently explained. The red 
oxide and varvicite occur as minerals; but of the whole 
series the peroxide is by far the most valuable. 


Peroxide of Manganese, MnO,=43°726, 
is found abundantly as a mineral, and passes in commerce 
under the name of black oxide of manganese, a name in- 
dicating its color. It is insoluble in water, and when ex- 
posed to a red heat gives off one fourth of its oxygen, 
forming the sesquioxide, as stated above, the action being 


How may manganese be obtained? What are its properties? How 
many oxides does it furnish? How may manganese be detected? What 
is the constitution of the peroxide ? 


COMPOUNDS OF MANGANESE. 275 


2(MnO,)... =... MnO, + O. 


On this fact is founded one of the processes for obtaining 
oxygen gas. Heated with hydrochloric acid, it yields 
chlorine, as has been explained. It was formerly called 
glassmakers’ soap, from the circumstance that it removes, 
when added to melted glass, the stain of protoxide of 
iron, by turning it into peroxide, and causes the glass to 
become colorless; but if too great a proportion of per- 
oxide of manganese is used, the glass assumes an ame- 
thystine color. 

Peroxide of manganese, when ignited with caustic pot- 
ash in a platina crucible, yields a substance known as 
Mineral Chameleon, which is of a green color. Water 
dissolves from it the Manganate of Potash, which is of 
a beautiful grass green, the solution speedily passing 
through a variety of shades of purples, blues, and reds. 
As yet, manganic acid is a hypothetical compound, and 
has not been insulated. When mineral chameleon is 
dissolved in hot water, a red solution is obtained of the 
Permanganate of Potash ; from the permanganate of ba- 
ryta a crimson solution of Permanganic Acid may be pro- 
cured by the aid of sulphuric acid ; but permanganic acid 
can not be obtained in the solid form. 

Among other compounds of manganese, the following 
may be named: 


Protochloride of manganese MnCl = 63°15. 
Perchloride “ 3 Mnz Cl; = 303°19. 
Perfluoride “ - Mn2F'l7 = 186°46. 


The protochloride may be made by acting on the per- 
oxide with muriatic acid, evaporating to dryness, and 
fusing at a red heat. On digesting with water, the proto- 
chloride dissolves, and any impurity of iron is left in the 
state of oxide. Then, by crystallizing, the chloride can 
be obtained in pink crystals. The perchloride is pro- 
duced when permanganate of potash, common salt, and 
sulphuric acid are heated. It is a dark greenish and 
volatile liquid. The perfluoride is obtained by distilling 
sulphuric acid, permanganate of potash, and fluor spar; 
it is a greenish yellow gas. 


What color does it give to glass? How is mineral chameleon made? 
What are its properties? Can manganic acid be insulated? How may 
the chlorides of manganese be formed? What are the properties of the 


fluoride ? 


276 IRON. 


SALTS OF THE PROTOXIDE OF MANGANESE. : 
Protosulphate of Manganese, formed by dissolving pro- 
toxide of manganese in sulphuric acid. The figure of its 
crystals depends on the temperature at which they were 
formed. They have a rose-colored tint. It is insoluble 
in alcohol, very soluble in water, and is used by the dyers 
to produce a fine brown color. 

There is but one sulphuret of manganese. It is ob- 
tained as a hydrate when manganese is precipitated by 
hydrosulphuret of ammonia (MnS, HO). It is of a flesh- 
red color. 


IRON. Fe= 28:00. 

TRon sometimes occurs in a native state and as mete- 
oric iron, also as oxide, carbonate, sulphuret, &c. It is 
one of the most abundant of the metals. Much of what 
is found in commerce is derived from clay iron-stone, 
which is an impure carbonate containing silica, alumina, 
magnesia, and other foreign substances. The native per- 
oxide of iron, red hematite; the hydrated peroxide, 
brown hematite; the black oxide, or magnetic iron ore, 
furnish some of the finer varieties of the metal. 

From clay iron-stone metallic iron is procured by the 
action of carbonaceous matter and lime at a high temper- 
ature. ‘The ore, having been roasted, is thrown into the 
furnace with coal and lime. Ifthe iron is im the ore asa 
silicate, the lime decomposes it at those high temperatures, 
forming a slag of silicate of lime, and the oxide of iron 
set free is instantly reduced by the carbonaceous matter ; 
the metal sinking down, protected by the slag, is let off 
by opening a hole in the bottom of the furnace. 

The substance thus produced is not pure iron; it con- 
tains carbon and other impurities, and passes under the 
name of cast or pig iron. It is purified by melting and 
sudden cooling, which converts it into fine metal ; this 
fine metal is then melted under exposure to air, which 
burns off the carbon as carbonic oxide, and the mass, 
from being perfectly fluid, becomes coherent. It is now 
subjected to violent mechanical action, such as hammer- 
ing or rolling; this forces out or burns off the impurities, 


What is the formation and use of the protosulphate of manganese ? 
What are the forms under which iron chiefly occurs? How is it obtain- 
ed from clay iron-stone? What is cast iron? By what processes is it 
converted into wrought iron ? a raat 


IRON. O77 


increases its tenacity, and it becomes the wrought iron of 
commerce. 

Cast Iron melts reaaily at a bright red heat, and expands 
in solidifying . on this depends its valuable application for 
making castings. Kept under the surface of salt water for 
a length of time, cast iron becomes converted into a body 
somewhat like plumbago, due, probably, to the removal 
of the iron as a chloride; the carbon which is left behind is 
sometimes observed, as it dries, to become hot: a phenom- 
enon to be accounted for by its porous state. ‘These facts 
have been frequently verified in the case of cannon which 
have lain for years at the bottom of the sea. There are 
two forms of cast iron, white and gray; the former con- 
tains about five per cent. of carbon, the latter three or four. 

Pure Iron may be obtained by decomposing precipitated 
peroxide of-iron by hydrogen gas, and melting the result. 
The metal has a bluish color, is more ductile than mallea- 
ble, and is the most tenacious of all bodies. It becomes very 
soft at a red heat, and possesses the welding property ; on 
this depends the art of forging it. Its specific gravity is 
77. Itis one of the few magnetic bodies, and, when soft, 
its magnetism is so transient that it may gain and lose that 
quality a thousand times in a minute. The melting point 
of iron is very high. In the mode of preparing it from 
cast iron it does not undergo the process of fusion, but its 
particles are simply welded together. The fibrous struc- 
ture which wrought iron possesses is the chief cause of its 
great tenacity; a wire th of an inch in diameter will 
bear a weight of 60 pounds. 

Steel, which is a valuable preparation of iron, is made 
by placing alternate strata of iron bars and charcoal pow- 
der in a close box and keeping them red hot. The pro- 
cess is known by the name of cementation. The iron 
gains about 1°5 per cent. of carson. Steel is much more 
fusible than iron, and becomes excessively hard and brit- 
tle by being brought to a red heat and then suddenly 
quenched in cold water. When allowed to cool slowly, it 
is quite soft, and various legrees of elasticity and hard- 
ness may be given to it by the process of tempering. 

By placing a piece of platina in nitric acid of a specific 


What are the properties of cast iron? What changes does it undergo 
under water? How may pure iron be obtained? What are its proper- 
ties? What is steel? How is it made, and what are its properties ? 


AA 


~ 


278 OXIDES OF IRON. 


gravity of 1:34, and then bringing an iron wire in contact 
with it and withdrawing the platina, the iron assumes a 
passive or allotropic state. It now exhibits no tendency 
to unite with oxygen, cannot precipitate copper from its 
solutions, and simulates the properties of platina and gold. 


LECTURE LXI. 


Tron.— Oxides of:— Three Oxides and Ferric Acid.— Tests 
Jor Iron.—Salts of the Protoxide and Peroxide-— The 
Sulphurets.—NickeL.—Its Reduction from the Oxalate. 
— Cosait. — Smalt. — Zaffre. — Sympathetic Ink. — 
Zinc.— Distillation of —Salts of the Protoxide. 


IRON AND OXYGEN. 

Iron burns with rapidity in oxygen gas, as may be 
Fig. 263. proved by igniting a piece of it in wire coiled 
into a spiral form in a jar of that gas (Fg. 263), 
when it will be found to take fire and burn beau- 
tifully. In atmospheric air, under favorable cir- 
cumstances, the combustibility of this metal may 
be proved. Thus, fine iron filings, sprinkled in 
the flame of a spirit lamp, burn with scintilla- 
tions; exposed to air and moisture, it slowly 
rusts. Iron yields four oxides : 


Protoxide=.' “oe... .heO = 26018. 
Black oxide. . . . Fe,O,=116°052, 
Peroxide... .Fe,O,== '80:089. 
Ferric acid { >... + |. feO, ==, 52039; 


Protoxide of Iron. FeO=36:013. 


This oxide has not yet been insulated, but it exists, 
united with acids, in an extensive series of salts, from 
which it is thrown down as a hydrate by alkalies, and is 
then of a white color, which darkens as it passes into the 
state of peroxide. Ferrocyanide of potassium gives a 
white precipitate, and the ferridcyanide a deep blue. Hy- 
drosulphuret of ammonia gives a black sulphuret of iron. 
Sulphureted hydrogen and gallic acid give no precipitate. 


How may iron be rendered passive? How may the rapid oxydation of 
iron be illustrated? How many oxides does this metal yield? What 
are the reactions which the protoxide furnishes with tests ? 


OXIDES OF IRON. 279 


Black Oxide of Iron. Fe,;0,=116°0852. 

This oxide, known also as the magnet or loadstone, is 
found as a mineral. It is a compound of the protoxide 
and peroxide. The scales of iron found in blacksmiths’ 
forges mainly consist of it. It may also be produced by 
decomposing the vapor of water by metallic iron in a red- 
hot tube. 


Peroxide of Iron, Fe,0;=80-039, 


is found in nature as oligist iron, or as a hydrate. Itmay 
be produced artificially as a hydrate by precipitation from 
a solution of persulphate of iron by a caustic or carbona- 
ted alkali, or in a pure state by igniting green vitriol; 
there is then left a red powder, known as rouge, used for 
polishing metals. This oxide is not magnetic; it is the 
basis of a series of salts which yield, with alkalies, a brown 
hydrated peroxide; with ferrocyanide of potassium, Prus- 
sian blue; with sulphocyanide of potassium, a blood-red 
solution; with tannin and gallic acid, a black. This last 
is of considerable interest, constituting the basis of ordi- 
nary ink. 

The presence ap iron can always be determined by 
passing it into the condition of peroxide, and applying the 
foregoing tests. 

Ferric Acid, FeO;=52:039, 

is prepared by heating peroxide of iron with four parts of 
nitrate of potash. The result is treated with cold water, 
which yields a red solution of the ferrate of potash. This 
slowly decomposes in the cold, and very rapidly when the 
solution is warm. ‘The ferrate of baryta precipitates 
when the potash solution is acted on by a soluble salt of 
baryta. It is a permanent body, of a crimson color. 

Among other compounds of iron, the following may be 
named : 


Protochloride. of iron. 2)... Satie, « eOd t= 63°47. 
Perchloride be Obs ba Sm Fes ly =e kOe ae 
Protiodide eel tite fi eh Erm loo ore 
Protosulphuret “ WA des pi ot dele bo Ae ke 
Sesquisulphuret “ Ve ite. eS JEM OgiN 30 at L436, 
Bisulphuret Md s Hee == G024. 


Under what natural forms does the black oxide occur? How may it be 
formed artificially ? What are the natural forms of the peroxide? How 
may it be prepared? For what purposes is itused? What is its action 
with reagents? What is common ink? How may the presence of iron 
be detected? What are the properties of ferric acid? Of the other com- 
pounds, mention some of interest. 


280 SALTS OF IRON. 


Of these, the protochloride is formed by passing hydro- 
chloric acid over red-hot iron. It is white, but forms a 
green solution in water. The perchloride, in solution, by 
dissolving peroxide of iron in hydrochloric acid. The 
protiodide, by boiling an excess of iron filings with iodine, 
and evaporating; it forms, on cooling, a dark gray mass. 
Its solution absorbs oxygen from the air. The protosul- 
phuret of iron, which is much used for forming sulphuret- 
ed hydrogen, may be made by heating a mass of iron to 
a white heat, and applying to it roll sulphur, and receiv- 
ing the melted globules in a bucket of water. It may 
also be procured by igniting iron filings with sulphur. 
The bisulphuret occurs abundantly as a mineral of a gold- 
en yellow color, crystallized in cubes or allied forms, and 
knownas Iron Pyrites. It frequently assumes the form of 
various organic remains, being one of the common petri- 
fying agents, but in this state differs essentially from the 
cubic pyrites, both in color and oxydizability, these fossil 
remains rapidly decaying under exposure to the air, but 
the other form being unacted on. Besides these, there is 
a sulphuret of iron which is magnetic. 


SALTS OF THE PROTOXIDE OF IRON. 
Carbonate of Iron may be obtained from the sulphate 
by an alkaline carbonate, falling as a whitish precipitate. © 
It turns brown, however, from the absorption of oxygen. 
It occurs as a mineral in spathic iron, and dissolves in 
water containing carbonic acid, forming chalybeate waters. 

Protosulphate of Iron—Copperas—Green Vitriol—is 
prepared largely by the oxydation of iron pyrites, and 
crystallizes in oblique prisms of a grass green color. It 
has a styptic taste, dissolves in twice its weight of cold, 
and three fourths its weight of boiling water. It contains 
five atoms of water. At alow red heat it becomes anhy- 
drous. In this state it is used for the manufacture of the 
Nordhausen sulphuric acid. 

SALTS OF THE PEROXIDE OF IRON. 

Persulphate of Iron may be formed by adding to a so- 
lution of the protosulphate of iron half an equivalent of 
sulphuric acid, and peroxydizing by nitric acid. ‘With 
water it forms a red solution. 


~ “What is iron pyrites? What is the difference of its forms? How is 
the carbonate of iron formed? What is the process for preparing the sul- 
phate? How is the persulphate obtained ? 


NICKEL AND COBALT. 281 


NICKEL. Ni = 295, ’ 

NickeEt may be obtained by igniting its oxalate in a coy- 
ered crucible, carbonic acid escaping, and the metal being 
reduced. 

NMO+0C,0,...=... M+2(CO,); 
one atom of the oxalate of nickel yielding one of the met- 
al and two of carbonic acid gas. 

Nickel is a white metal, requiring a high temperatura 
for fusion. It is magnetic, and has a specific gravity of 
8:5. It is commonly associated with iron in meteorites, 
and enters into the composition of German silver ; unites 
with oxygen, forming a protoxide and sesquioxide, the 
former yielding salts of a green color; the latter is an in 
different body. 

SALTS OF THE PROTOXIDE OF NICKEL. 

Sulphate of Nickel crystallizes from its solutions witk 
six atoms of water in slender green prisms, which, wher 
exposed to the sun, change into an aggregate of octahe 
drons, becoming opaque. 

Nickel is chiefly used in the preparation of German 
silver, an alloy of copper, zinc, and nickel. It is of a 
white color, takes a good polish, and is malleable. 

COBALT, Co = 2955, 

is generally associated with iron and nickel, and with 
them occurs in meteoric iron. Like the preceding metal, 
it may be obtained by igniting its oxalate in a covered 
crucible, carbonic acid being disengaged and metallic 
cobalt left. It is a pinkish white metal, requiring a high 
temperature for fusion. Its specific gravity is 7:8. It is 
magnetic, as recent experiments have proved. It forms 
a protoxide and a sesquioxide, the former being the basis 
of a class of salts which are chiefly of a pink or blue col- 
or. Smalt is a silicate of cobalt, and Zaffre an impure 
oxide ; the former is used to communicate to paper a faint 
blue tinge, and the-blue color which the oxide gives to 
glass is taken advantage of in coloring the common vari- 
eties of earthen-ware. Cobalt is easily detected upon this 
principle. 

By what process is nickel obtained? What are its properties? Under 
what remarkable circumstances does it occur with iron? What change 
does the sulphate of nickel undergo in the sunlight? How is cobalt pro- 


cured? Is it magnetic like nickel? What is smalt? What is zaftre ? 
What are the uses of cobalt? 
Aa2 


282 ZINC. 


The chloride of cobalt may be made by dissolving the 
oxide or the metal in hydrochloric acid. It is a pink 
solution, which turns blue when dried. It forms a beau- 
tiful sympathetic ink, for letters written with it, especially 
on paper which has a pinkish tinge, are entirely invisible, 
but become of a bright blue color when the paper is 
warmed, the letters again fading as they become cool and 
moist. 


ZINC. Zn = 32'3. 
Zinc is a very abundant metal, immense quantities of 
it occurring in the state of New Jersey and in various 

Fig.964, Other places. From zinc blende, which is a sul- 
phuret, converted by roasting into an oxide, or 
| from the carbonate brought into the same state 

by ignition, the metal may be obtained by the 
process of distillation by descent. The ox- 
ide, mixed with charcoal, is introduced into a 
crucible which has an iron tube passing through 
a hole in its bottom, as seen in Fug. 264, and 
the lid being luted on, the temperature is raised 
to a white heat, and the zinc, distilling over, 
may be condensed in water. 

Zinc is a bluish-white metal, which melts at about 770° 
F., and, if exposed at a bright red heat to the air, takes 
fire and burns with a brilliant pale green flame. Its spe- 
cific gravity is about 7:00. At common temperatures it is 
brittle, but it may be rolled into thin sheets at about 300° 
F., and then retains its malleability when cold. During 
its combustion there arises from it a great quantity of 
flocculent oxide, which formerly went under the name 
of nxzhel album, or philosopher’s wool. Among the com- 
pounds of zinc may be mentioned 


Protoxide of:zine- .« ... . - ZnO’ = 40°313; 
Chloride W Se te 6 RARE SHG 
Sulphuret af se gk) euler ae 4, 


Of these, the oxide is formed, as has been said, during 
the combustion of zinc. It is also precipitated as a white 
hydrate from its soluble salts by potash or soda, soluble 
in excess of the precipitant. The chloride may be made 
by the action of hydrochloric acid on metallic zinc. It is 


What property does the chloride possess? By what process is zinc ob- 
tained? Is there any connection between its ductility and temperature ? 
During combustion, what arises from it? How may it be detected? 


CADMIUM.—TIN. 283 


used in the arts for soldering under the name of butter of 
zinc. The sulphuret occurs as a mineral under the name 
of zinc blende. 


SALTS OF THE PROTOXIDE OF ZINC. 

Sulphate of Zinc— White Vitriol.—This salt is formed 
in the process for procuring hydrogen gas by the action 
of dilute sulphuric acid on zinc. It crystallizes in color- 
less prisms with six atoms of water, and is soluble in two 
and a half parts of cold water. It has a styptic taste, 
and reddens vegetable blues. There are three different 
subsulphates of this oxide. 

Silicate of Zinc, the electric calamine of mineralogists ; 
remarkable for becoming electric when heated. 


LECTURE LXII. 


Capmium.—Sources of —Its Volatility —Ti1n.— Block and 
Grain.—Its Properties —Protoxide and Stannic Acid.— 
Chlorides of Tin.— Mosaic Gold.— Its Uses——Curo- 
mium. — Chromiron.— Green Oxide and its Uses.— 
Chromic Acid.— Salts of the Sesquioxide.— Salis of 
Chromic Acid.— Other Metals —Tiranium. 


CADMIUM. Cd = 55°8. 

Capmium usually occurs associated with zinc as a car- 
bonate. In the preparation of that metal by distillation, 
as has been described, the cadmium first comes over. 
From any impurity of zinc it may be separated by pre- 
cipitation from an acid solution by sulphureted hydrogen, 
which throws the cadmium down as a yellow powder, 
put does not act onthe zinc. ‘The sulphuret of cadmium 
is then dissolved in nitric acid, the oxide precipitated by 
potash, and, when dry, reduced by charcoal. The com- 
pounds of cadmium are not important. The metal itself 
is very volatile. 

TIN. Sn = 57°9. 

Tin occurs as an oxide in England, Mexico, Germany, 
and the East Indies. It may be reduced by the action 
of charcoal at a high temperature. It is found in com- 


How is white vitriol prepared? What is electric calamine? Under 
what circumstances does cadmium occur? What are the native forms of 
tin ? 


284 COMPOUNDS OF TIN. 


merce under two forms, block tin and grain tin. Ifa bar 
of tin is heated, the purer parts, being the more fusible, 
ooze out of it, constituting grain tin, and the mass which 
is left behind is block tin. 
Tin is.a white metal like silver. It oxydizes in the air 
superficially, the action ceasing as soon as a thin crust is 
formed. At a red heat it oxydizes rapidly, forming putiy 
powder, used for polishing metals. It is very malleable, 
and may be rolled into thin foil. When bent backward 
and forward it emits a crackling sound. It is very soft; 
its specific gravity 7°2. It melts at 442°, and burns when 
raised to a high temperature in the air. Some of its com- 


pounds are 
Prowx1de Of tint ss ee OU eS bola. 
Sesquioxide 9. ss (Sa, Os 129:839 
Peroxide pid con Gis, cates WO oe B38 020, 
Protochloride sn eas <li 4s. 2 ISROL] see 9331, 
Perchiqnds 9 to ae Cle = Lee. 7A. 
Protosulphurett} ia. ke? 2. Saba re 
Persulphuret . .. . SZuS eee el 


The protoxide may be made by precipitation from the 
protochloride by carbonate of potash. It.is to be washed 
with warm water, and its water finally driven off in a cur- 
rent of carbonic acid gas at a red heat. It is of a black 
color, is easily set on fire in atmospheric air, passing into 
the condition of peroxide. Its salts reduce the noble 
metals to the metallic state, when added to their solutions, 
and yield with the chloride of gold the Purple of Cassius. 
The peroxide, calléd also stannic acid, from exhibiting 
weak acid properties, may be made by the action of ni- 
tric acid on tin. It is a hydrate in the form of a white 
powder, insoluble in acids and water; but if obtained by 
precipitation from perchloride of tin, it is soluble both in 
acids and alkalies. Melted with glass, it forms a white 
enamel. 7 

The protochloride may be made by dissolving tin in 
warm hydrochloric acid. The solution, when concentra- 
ted, deposits crystals of the hydrated protochloride. These 
are decomposed when heated. The anhydrous protochlo- 
ride may be had by passing hydrochloric acid gas over 
metallic tin at a red heat. ‘The perchloride is procured 


What are block and graintin? What arethe properties of tin? When 
a bar of tin is bent backward and forward, what phenomenon arises ? 
How is the protoxide made, and how do its salts act on those of the noble 
metals? How is stannic acid prepared? What does it yield with glass? 


CHROMIUM. 285 


by distilling eight parts of tin with twenty-four of corro- 
sive sublimate. It is a smoking fluid, and was formerly 
called the Fuming Liquor of Libavius. A solution of 
this substance, much used in dyeing, is made by dissolving 
tin in nitromuriatic acid, or by warming a solution of the 
protochloride with a little nitric acid. 

Of the sulphurets, the first may be formed by pouring 
melted tin on sulphur, and igniting the powdered result 
with more sulphur in a crucible. It is a bluish gray com- 
pound. The persulphuret is obtained when two parts of 
peroxide of tin, two of snlphur, and one of sal ammoniac 
are ignited in a retort. It is a body of a golden yellow 
color, formerly called Aurum Musivum, ov Mosaic gold, 
in small scales of a greasy feel, and is used for exciting 
electrical machines, being much more energetic than the 
common amalgam, though less durable in its power. 

Tin furnishes several valuable metallic combinations ; 
Tin Plate is sheet iron superficially alloyed with it. 
The soft solders are alloys of lead and tin. Pewter is an 
alloy with antimony. 


CHROMIUM. Cr=28. 

Curomium occurs abundantly near Baltimore as the 
chromate of iron (Chrome Iron), more rarely as the red chro- 
mate of lead. The metal may be obtained by the action 
of charcoal on the oxide at a high temperature, and is of 
a yellowish-white color. It takes its name from its tend- 
ency to produce highly colored compounds. It is very 
infusible, and has a specific gravity of about 6:00. Its com- 
pounds, to be here described, are 


Sesquioxide of chromium . . . . Cr,O3;= 80°039: 
Chromic acidty.. ) Us, ef a Norah 3) OTUs ro jDe Uae 
Sesquichloride of chromium . . . Cr,O3 = 162'26. 


The sesquioxide may be prepared by heating the chro- 
mate of mercury to redness in a crucible. The mercury 
is driven off, and the chromic acid partially deoxydized, 
leaving a beautiful grass-green powder, the sesquioxide. 
It may also be obtained by heating the bichromate of pot- 
ash red-hot, and washing the residue in water; also as a 
hydrate, by boiling a solution of bichromate of potash with 


What is the fuming liquor of Libavius? How is mosaic gold made, 
and what is its use? What alloys does tin furnish? Under what forms 
does chromium occur in nature? How is its sesquioxide prepared, and 
what is its use? 


286 COMPOUNDS OF CHROMIUM. 


muriatic acid, and adding alcohol; the mixture becomes 
of a green color, and ammonia precipitates the hydrated 
sesquioxide. It is a weak base, yielding a class of salts 
of a blue or green color. In the state of hydrate it is sol- 
uble in acids ; but, on making it red hot, it suddenly be- 
comes incandescent, passes into another allotropic state, 
and is now insoluble. This sesquioxide is isomorphous 
with the sesquioxides of iron and alumina. In its two al- 
lotropic states, it yields corresponding classes of salts, one 
of which is green, and the other reddish green. It is used 
for communicating a green color to porcelain. 

Chromic Acid may be made by adding one volume of a 
saturated solution of bichromate of potash to one and a 
half of oil of vitriol. On cooling, red crystals of chromic 
acid are deposited. It is isomorphous with sulphuric acid, 
produces with bases yellow and red salts, is a powerful 
oxydizing agent, is decomposed by a red heat into the ses- 
quioxide, destroys the color of indigo and other dyes, 
and may be detected by producing with the salts of lead, 
chrome yellow, and by its ready passage, under the influ- 
ence of deoxydizing agents, into the sesquioxide. 

The sesquichloride is procured when chlorine is passed 
over a mixture of the sesquioxide and charcoal in a red- 
hot tube. It is a lilac-colored body, which forms a green 
solution in water. There is also an oxychloride, which 
may be distilled as a deep-red liquid from a mixture of 
chromate of potash, common salt, and oil of vitriol. The 
fluoride, which is a red gas, is obtained by distilling in a 
silver retort a mixture of chromate of lead, fluor spar, and 
oil of vitriol. It is decomposed by the moisture of the air, 
forming chromic and hydrofluoric acids. 


SALTS OF THE SESQUIOXIDE OF CHROMIUM. 

Sulphate of Chromium and Potash—Chrome Alum.— 
When the oxide of chromium is dissolved in sulphuric 
acid and mixed with the sulphate of potash and a little 
free sulphuric acid, crystals of chrome alum are deposit- 
ed in red or blue octahedrons. The sulphate of chromium 
alone does not crystallize. 

Chrome Iron, a compound of the sesquioxide of chro- 
mium and the protoxide of iron, is found native, crystal- 


are the chloride and fluoride obtained? What is the form of the latter 
body? What is chrome alum? 


SALTS OF CHROMIC ACID. 287 


lized in octahedrons, and alsomassive. It furnishes most 
of the compounds of chromium. 


SALTS OF CHROMIC ACID. 

Chromate of Potash may be made by igniting chrome iron 
with one fifth its weight of nitrate of potash. It crystal- 
lizes in small, lemon-yellow prisms, and is very soluble 
in hot water. The crystals are anhydrous. 

Bichromate of Potash may be prepared from the for- 
mer by adding an equivalent of acetic acid: it crystal- 
lizes in prisms of a ruby red. Large quantities are con- 
sumed by dyers. 

Chromate of Lead—Chrome Yellow, obtained by pre- 
cipitation from either of the foregoing salts by a soluble 
salt of lead. It is used as a paint. 

Dichromate of Lead is formed by adding chromate of 
lead to melted nitrate of potash, and dissolving out the 
chromate of potash and excess of nitre by water. It is of 
a beautiful red color. 

The following metals, Vanapium, TunestTeN, Motys- 
DENUM, Osmium, and CoLuMBiuM, are not applied to any 
purposes in the arts, or are so rare as not to be of general 
interest. Trrantum might be included in the same obser- 
vation ; it is, however, deserving of remark as being a red 
metal like copper, and titanic acid, one of its oxygen com- 
pounds, is used in the coloring of artificial teeth. 


LECTURE LXIII. 


ArsEnic.—Preparation of the Metal—Properties of Ar- 
senious Acid.— Two Varieties of 1t.— Two methods of 
detecting wt.—Process in Cases of Poisoning —Sulphur- 
eted Hydrogen Test —Marsh’s Test— The Copper Test. 
— Difficulties arising from Antimony. 

ARSENIC, As = 37°7. 
ARSENIC is obtained by sublimation in a current of air 
of the arseniuret of cobalt and iron, the vapor condensing 
as a white oxide. This being mixed with powdered char- 


What is the constitution of the two chromates of potash? What is 
chrome yellow? What is the color of titanium? From what substanoes, 
and in what manner, is arsenious acid prepared ?. 


258 OXIDES OF POTASSIUM. 


KOGG.+-;:Ca0, 10%. .=:.3 Ca0, CO; + KORO 


that is, the lime takes carbonic acid from the carbonate of 
potash, and the oxide of potassium unites with water. The 
solution may be known to be free from carbonic acid by 
not effervescing when mixed with stronger acids. 

The hydrate of potash is a white solid, having a power- 
ful affinity for water, and abstracting it rapidly from the 
air. ‘Taken between the fingers, it communicates to the 
skin a soft feel, and, if a-concentrated solution be used, 
soon effects a disorganization; hence it is used by sur- 
geons in the form of small sticks as an escharotic. It 
possesses pre-eminently the alkaline qualities, and, indeed, 
may be taken as the type of that class of bodies, neutral- 
izes the most powerful acids perfectly, and communicates 
to turmeric paper, or turmeric solution, a brown tint. It 
turns the infusion of red cabbage green, and, possessing 
an intense affinity for carbonic acid, is used in organic 
analysis to absorb that gas. 

Potash in combination occurs in all fertile soils, and is 
essential to the growth of land plants, from the ashes of 
which its carbonate is abundantly procured. This may be 
shown by filtering water through the ashes of wood, when 
the clear liquid will be found to answer to all the tests in- 
dicating the presence of potash. It occurs also abundant- 
ly in feldspar, and hence is found in clays. The want of 
fertility in soils appears occasionally to be due to the ab- 
sence of this body. 

The bichloride of platinum gives, with a solution of 
potash, a yellow precipitate of the chloride of platinum 
and potassium. When the amount of potash is small, it 
is well to add alcohol at first, in which the double chlo- 
ride is insoluble. Ammonia yields a similar precipitate ; 
but this may be avoided by exposing the substance, in the 
first instance, to a red heat before testing. Perchloric acid, 
with alcohol, yields a white precipitate. ‘Tartaric acid, 
if added in excess, and the mixture stirred with a glass 
rod, bearing gently on the sides of the vessel, gives white 
streaks of the bitartrate of potash wherever the rod has 
passed over the glass. 


Of what properties is the hydrate of potash possessed, and what are its 
uses? How may the existence of potash in the ashes of plants be proved? 
What are the tests for the presence of this substance ? 


COMPOUNDS OF POTASSIUM. 259 


Of other compounds of potassium, the followmg may be 


mentioned : é 
Peroxide of potassium, K O3. Bromide of potassium, KBr. 
Chloride of potassium, KCl. Protosulphuret of potassium, KS, 
Iodide of potassium, KJ. Pentasulphuret of potassium, K S5. 


It also combines with hydrogen in two proportions, pro- 
ducing a solid and a gas, the latter of which takes fire 
spontaneously in the air. 

Of these compounds, the most important are the per- 
oxide of potassium, which is formed by passing oxygen 
over red-hot potash; it is decomposed by water, evolving 
oxygen and producing potash; the chloride of potassium, 
which is analogous to common salt; the iodide, much of 
which is consumed in medicine, under the name of hy- 
driodate of potash. It may be prepared by dissolving 
iodine in a solution of potash, till the liquid begins to ap- 
pear brown, then evaporating to dryness, and igniting the 
residue: oxygen is evolved, and iodide of potassium re- 
mains; it may be then dissolved in water, and crystal- 
lized. It is white, crystallizes in cubes, and is very sol- 
uble in water and hot alcohol. Its solution will dissolve 
large quantities of iodine. The pentasulphuret is the chief 
ingredient of liver of sulphur, which is formed by fusing 
sulphur with carbonate of potash at a low temperature. 


SALTS OF THE PROTOXIDE OF POTASSIUM. 

Carbonate of Potash is obtained by lixiviating the ashes 
of plants. In an impure state it forms the potashes and 
pearlashes of commerce. It may be obtained pure by ig- 
niting the bitartrate with half its weight of the nitrate of 
potash. It has an alkaline taste, its solution feels greasy 
to the fingers, it is very soluble in water, and deliquescent. 

‘ Bicarbonate of Potash, formed by transmitting a stream 
of carbonic acid through a solution of the former salt. It 
crystallizes in eight-sided prisms with dihedral summits. 

Sulphate of Potash, formed by neutralizing the follow- 
ing salt. Crystallizes in anhydrous, oblique, four-sided 
prisms, soluble in about ten times its weight of water. 

Sulphate of Potash and Water, sometimes designated 
as the bisulphate of potash ; it is the residue of the produc- 
tion of nitric acid. It is soluble in water, and has an acid 
reaction. It crystallizes in rhombohedrons. 


Name some of its other compounds. What are the properties of the 
iodide? From what is the carbonate obtained ? 


260 SALTS OF POTASH. 


Nitrate of Potash is extracted on the large scale from 
certain soils in which organic matter is decaying in con- 
tact with potash. It crystallizes in six-sided prisms, fuses 
at a heat beneath redness, with evolution of oxygen gas. 
It is soluble in about three times its weight of water, at 
common temperatures. ‘This salt enters as an essential 
ingredient in gunpowder, which is composed of,about one 
atom of nitrate of potash, one of sulphur, and three of 
carbon. The sulphur of this mixture accelerates the com- 
bustion, while the oxygen of the nitre forms carbonic acid 
with the charcoal. ‘The products, therefore, of the per- 
fect combustion of gunpowder are carbonic acid, nitrogen, 
and the sulphuret of potassium. It commonly happens, 
however, that sulphate of potash is formed. The pro- 
portions of the ingredients of gunpowder are varied for 
different uses. The powder used for mining, for exam- 
ple, contains more sulphur than that used for firearms. 

Chlorate of Potash—When a stream of chlorine is 
passed into a solution of potash, the chloride of potassium 
and the chlorate of potash result; the latter is deposited 
in flat, scaly crystals. 

The chlorate of potash contains no water ; it dissolves 
in about fifteen times its weight of that fluid; melts at a 
red heat, with evolution of pure oxygen; deflagrates with 
combustible bodies, sometimes with much violence. 


LECTURE LVIII. 


Sopium.—-Preparation of.—Relation to Oxygen and Wa- 
ter —Color communicated to Flame.—Its Oxides — The 
Hydrated Oxide— Tests for Sodium—Haloid Com- 
pounds——Common Salt.-—Salts of the Protoxides, Car- 
bonates, Sulphates, Nitrates, §c. Liratom.—Barivm. 
—Its Oxides.—Haloid Compounds.—Salis of the Pro- 
toxide. 

SODIUM. Na = 23:3. 
Sop1um may be obtained by the same process as potas- 
sium, but is best procured by igniting the calcined acetate 
of soda with powdered charcoal in an iron bottle; and, as 


y . 
What is the origin and use of the nitrate? How is the chlorate made ? 
How is sodium obtained, and what are its uses? 


OXIDES OF SODIUM. 261 


the sodium does not act upon carbonic oxide, the opera- 
tion is much more productive than in the case of the oth- 
er metal. Like potassium, it is to be kept in bottles un- 
der the surface of naphtha. ° 

In color, sodium resembles silver ; its specific gravity is 
0:9348; it therefore floats upon water. It melts at 194° 
F., and is more volatile than potassium. Thrown upon 
water, it decomposes it with a hissing sound, and with the 
evolution of hydrogen, but no flame appears. If, howev- 
er, the water is hot, then a beautiful yellow flame, char- 
acteristic of sodium and its compounds, is the result. 


SODIUM AND OXYGEN. 
With oxygen sodium forms three compounds : the sub- 
oxide, protoxide, and peroxide. 


Protoxide of Sodium. NaO = 31°313. 


This, like the corresponding potassium compound, is 
produced by oxydizing sodium in dry air. It is a white 
powder, which attracts moisture from the air and forms the 
hydrated oxide of sodium, commonly called caustic soda. 


Hydrated Oxide of Sodium, NaO + HO = 40°323, 


or caustic soda, may be made by the same process as that 
given for caustic potash, by using carbonate of soda, and, 
when the resulting carbonate of lime has settled, evapo- 
rating the liquid. ‘The best proportions are one part of 
quicklime to five of carbonate of soda in crystals. 
Caustic soda resembles caustic potash in most of its 
properties. It is deliquescent, has a strong affinity for 
arbonic acid, and acts upon animal tissues as an escha- 
rotic. Its salts are generally more soluble than the pot- 
ash salts, and on this are founded the methods recom- 
mended for distinguishing the latter compounds from it. 
Moreover, the soda compounds communicate to the flame 
of alcohol, or to the blow-pipe flame, a yellow color: the 
same tint which is characteristically seen when sodium 
is placed in hot water. 


Chloride of Sodium. NaCl = 58°77. 


The chloride of sodium, common salt, is obtained abund- 
antly from the waters of the sea, to which it gives their 


What are its properties compared with potassium? What compounds 
with oxygen does it give? How is caustic soda obtained? What are its 
properties anduses? What color do the sodium compounds give to flame ? 


262 CHLORIDE OF SODIUM. 


salinity. It is also found as rock salt, deposited exten- 
sively in certain geological formations. 

Common salt is the general type of that extensive class 
of compounds which have derived the name of salt bodies 
from it. It crystallizes in cubes, and, when in mass, is 
often perfectly transparent, and permits the passage of 
heat of every temperature through it freely. It melts into 
a liquid at a red heat, crystallizes in cubes, and is not 
more soluble in hot than cold water. It is extensively 
used in the preparation of hydrochloric acid and chlo- 
rine; immense quantities, also, are annually consumed in 
the preparation of carbonate of soda, which is made by 
first acting on the common salt with oil of vitriol, so as to 
turn it into sulphate of soda, and igniting this with char- 
coal and carbonate of lime: an impure carbonate of soda 
is the result, known under the name of black ash, or Brit- 
ish barilla. Common salt is extensively used for the 
curing of meat. It is also an essential article of food, 
being decomposed in the animal system, and furnishing 
hydrochloric acid to the gastric juice and soda to the bile. 

The compounds of sodium with bromine, iodine, sul- 
phur, &c., are not of interest. 


SALTS OF THE PROTOXIDE OF SODIUM. 

Carbonate of Soda is sometimes obtained by lixiviating 
the ashes of sea-weeds. Large quantities are also pro- 
cured from the decomposition of sulphate of soda by saw- 
dust and lime at a high temperature, the carbonaceous 
matter decomposing the sulphuric acid and generating 
carbonic acid, which unites with the soda, while the liber- 
ated sulphur is partly dissipated and partly unites wit 
the calcium. From the resulting mass carbonate of soda 
is obtained by lixiviation. The crystals, as found in com- 
merce, contain generally ten atoms of water; there are: 
two other varieties, the one containing eight atoms, and 
the other one atom of water. Large quantities of the 
carbonate of soda are also sold in an uncrystallized state, 
under the name of salts of soda. The figure of the crys- 
tals of this salt is a rhombic octahedron. They effloresce 
on exposure to the air. They are soluble in five times 


What is the constitation of common salt? From what sources is it de- 
rived? What are its properties? How is barilla obtained from it? 
Why is it essential as an article of food? From what source is the car- 
bonate of sodaobtained? Describe the preparation of it from the sulphate. 


SALTS OF SODA. 263 


their weight of cold and in less than their own weight of 
boiling water. 

Bicarbonate of Soda, or the double carbonate of soda 
and water, is formed by transmitting a stream of carbonic 
acid through a solution of the carbonate, and is in. the 
form of a white powder. It is less soluble in water than 
the former. There is a sesquicarbonate, which passes in 
commerce under the name of trona. 

Sulphate of Soda is the Glauber’s salt of the shops; oc- 
curs as a natural product, and also as the result of the 
preparation of hydrochloric acid. It is in prismatic crys- 
tals of a bitter taste, efflorescing in the air, and becoming 
anhydrous. Water dissolves more than half its weight 
of this salt at 911° F., but above that degree it is less sol- 
uble. When a solution of three parts of this salt in two 
parts of water is corked up in a flask while boiling, it may 
be cooled without crystallization taking place; but if the 
cork is withdrawn, crystallization commences at once, or 
if it does not, the introduction of any solid matter produ- 
ces it, and the temperature of the solution at once rises. 

Nitrate of Soda is found abundantly in different parts 
of America in the soil; it crystallizes in rhomboids, dis- 
solves in twice its weight of cold water, and, from its del- 
iquescence, can not be used in the manufacture of gun- 
powder. 

Phosphate of Soda (tribasic) is formed by neutralizing 
phosphoric acid with carbonate of soda; two of the hy- 
drogen atoms are replaced; it crystallizes in oblique 
rhombic prisms, dissolves in three times its weight of cold 
® water, is of an alkaline taste, and gives a lemon-yellow 
precipitate with nitrate of silver. By the addition of soda 
to it a subphosphate is formed, in which all three of the 
hydrogen atoms of the acid are replaced; but by the ad- 
dition of phosphoric acid to the ordinary phosphate, till it 
ceases to give any precipitate with chloride of bariam, the 
biphosphate of soda results, a salt very soluble in water. 
Its crystals are rhombic prisms. In it only one of the hy- 
drogen atoms is replaced. 

Macrocosmic Salt, or the phosphate of soda, ammonia, 


What is the commercial name of the sulphate? What peculiarity is 
there in the crystallization of its solution? Why can not the nitrate be 
used for gunpowder? What is the difference between the phosphate, 
the pyrophosphate, and the metaphosphate of soda ? 

S 


264 LITHIUM. 


and water, is made by dissolving seven parts of phosphate — 
of soda in two parts of water, and adding one part of sal am- 
moniac. Ata low heat it parts with its water of crystal- 
lization, and the temperature rising, it loses its ammonia 
and saline water, becoming monobasic phosphate of soda. 
It is much used in blow-pipe experiments. 

Pyrophosphate of Soda (bibasic) is procured by heating 
the phosphate. It gives a white precipitate with nitrate 
of silver. 

Metaphosphate of Soda (monobasic) is formed by heat- 
ing microcosmic salt to redness. It is soluble in water, 
melts at a red heat, and gives, with dilute solutions of the 
earthy and metallic salts, viscid precipitates. 

Biborate of Soda, the borax of the shops. _ It is import- 
ed in a crude state from the East Indies, and manufac- 
tured from the natural boracic acid of - taly by the addi- 
tion of carbonate of soda. It crystallizes in octahedrons, 
or in oblique prisms, the former containing five, the latter 
ten atoms of water, all of which is lost by exposure to a 
red heat, the salt then fusing into a glass. It is of great 
use in blow-pipe experiments. 

LITHIUM. L=6-42. 

This rare metal occurs in certain minerals, such as 
spodumene, lepidolite, &c. It is a white metal, commu- 
nicating to flame a red color. It yields a protoxide the 
carbonate of which is of sparing solubility in water; thus 
forming the link of connection between the potash and 
soda carbonates, which are very soluble, and the carbon- 
ates of the alkaline earths, as baryta and strontia, whic 
are insoluble. 

This brings us to the metals of the alkaline earths, which 
form a division of our first group; the first of these is 


BARIUM. Ba=68°7. 

The existence of barium was first proved by Davy, who 
isolated it by electrifying mercury in contact with the hy- 
drate of baryta, an amalgam formed, from which the mer- 
cury was subsequently distilled, leaving the barium as a 
metal of a gray color like cast iron, heavier than sulphuric 
acid, in which it sinks, obtaining oxygen rapidly from the 

What is microcosmic salt? From what source is borax derived, and 
what are its uses? In what minerals does lithium occur? What is the 


relation of its carbonate to those of the preceding and subsequent metals ? 
How was barium first obtained ? 


OXIDES OF BARIUM. 265 


air, and giving rise to the production of the protoxide of 
barium, baryta. 


Protoxide of Barium, BaO = 76°713, 
may be obtained by igniting the nitrate of baryta, the de- 
composition being. 
BaO, NO,;...=...BaO+ NO,+ O; 


that is, one atom -of nitrate of barytes yields one of pro- 
toxide of barium, and one of nitrous acid and one of oxy- 
gen gas are expelled. 

This protoxide is a white colored body, possessing a 
strong affinity for water, with which it exhibits the phe- 
nomenon of slacking, as is the case to a less extent with 
lime, heat being evolved. It has an acrid taste, is soluble 
in water, and absorbs carbonic acid from the air. Its 

grayity is about 4-000. Its soluble salts are pois- 

a 

ydrate of Baryta, BaO, HO = 85°726, 
is formed by slacking the protoxide, and is a white pow- 
der, very soluble in hot, but less so in cold water, yield- 
ing, therefore, crystals when a hot solution cools: these 
contain nine atoms of water of crystallization. The cold 
solution is used as atest for carbonic and sulphuric acids, 
with which it forms insoluble white precipitates. 

This solution is most easily obtained by calcining the 
native sulphate with pulverized charcoal, which converts 
it into the sulphuret of barium. ‘To a boiling solution of 
this body oxide of copper is added till the liquid ceases to 

acken a solution of acetate of lead. On being filtered, 
the solution of hydrate of barytes is obtained. 


Peroxide of Barium, BaO, = 84°7, 


is made by igniting chlorate of potash with barytes, or by 
passing oxygen over barytes in ared-hot tube. It is used 
in the preparation of peroxide of hydrogen. 

Of the other compounds of barium, the chloride is much 
used as a test for sulphuric acid; it may be made by de- 
composing carbonate of baryta by hydrochloric acid. The 
sulphuret of barium is made by igniting the sulphate of 


~ What is the process for obtaining the protoxide, and also its hydrate? 
What acids is a solution of baryta used to detect? How is the peroxide 
made? What is its use? For what purpose is the chloride of barium 
employed ? 

Z 


ar 
ih 


266 STRONTIUM. 


baryta, heavy spar, with charcoal, which deoxydizes both 
the sulphuric acid and the baryta. It dissolves in hot wa- 
ter, and from this solution a solution of caustic baryta 
may be obtained by boiling with the oxides of lead or 
copper, and separating the sulphurets of those metals by 
filtration. By acting upon it with hydrochloric or nitric 
acid, the chloride or nitrate of baryta may be prepared. 


SALTS OF PROTOXIDE OF BARIUM. 

Carbonate of Baryta is found native, as the mineral 
Witherite, and may be prepared by precipitating a solu- 
ble salt of baryta with an alkaline carbonate. It is solu- 
ble in 4300 times its weight of cold water, and 2300 of 
boiling water. 

Sulphate of Baryta, found native abundantly as heavy 
spar, and from it most of the compounds o. barium are 
prepared. It is called heavy spar, its density bei ing 4°47. 
It crystallizes generally in tabular plates, and is wholly 
insoluble in water. Mea <— 


‘- 


LECTURE LIX. 


Strontium.— Uses in Pyrotechny.—Salts of Protowide— 
Catcium.—Protoxide of——Sources in Nature.— Tests 
for.—Haloid Compounds, Chloride, Fluoride, Sulphur- 
ets, &c.—WSalts of the Protoxide, Carbonate, Sulphate, 
Phosphate, Chloride—Maenrsium.—Protoxide.—Salts 
of Protoxide, Carbonate, Sulphate, Double Phosphate. 
—A.uminum.—Sesquioxide.— Uses in the Arts.— Tes 
—Salts of the Sesquioxide, Double Sulphate, Alum— 
Manufacture of Porcelain and Glass.—Other Metals. 


STRONTIUM. Sr=43°8. 

Tis metal may be obtained by the same processes 
which have been used for obtaining barium, with which | 
it has a considerable analogy. Its natural compounds are 
the sulphate and carbonate, from which its other prepara- 
tions may be obtained. 

Strontium yields a protoxide, which is the basis of a 
series of salts, differing from baryta salts in not being 


How m __ How may the sulphate of barytes be converted into the sulphuret of 
barium ? hat are the properties of the carbonate and sulphate of ba- 
ryta? In what respect does strontium differ from barium ? 


CALCIUM. | 267 


poisonous. The chloride and nitrate are used in pyro- 
techny for the purpose of communicating to flame a brill- 
iant crimson color. The red fire of theatres contains the 
latter salt, and the former, if dissolved in alcohol, com- 
municates to its flame the characteristic test of the stron- 
tlum compounds. 
SALTS OF THE PROTOXIDE OF STRONTIUM. 
Carbonate of Strontia is the strontianite of mineralogists. 
Sulphate of Strontia is the celestine of mineralogists. 
It is not so heavy as sulphate of baryta, and is said to be 
soluble in about 4000 times its weight of boiling water. 

Nitrate of Strontia forms an ingredient of the red fire 
used in theatres; it crystallizes in octahedrons, and is 
soluble in five times its weight of cold water and half its 
weight of boiling water. 


CALCIUM. Ca=20'5. 

Caucium has neverbeen obtained in quantities sufficient 
to permit a full examination of its properties. It oxydi- 
zes with rapidity, yielding a protoxide, known also as 
quicklime or lime. 

Lime occurs as a carbonate in the various limestones, 
marbles, chalks, &c., which form in many countries ex- 
tensive mountain ranges. Its other salts are very abund- 
ant. 

From the carbonate, pure or quicklime may be ob- 
tained by exposure to a bright red heat. If the limestone 
contains silica, it may, however, be overburnt, a silicate 
of lime forming, which prevents the product from slacking. 
It possesses a strong affinity for water, and unites there- 
with with a great elevation of temperature, as exhibited 
in the process of slacking. Exposed to a high tempera- 
ture, it phosphoresces splendidly. The hydrate which 
forms when lime is slacked is white; itis soluble to a small 
extent in water; and it is remarkable that cold water 
dissolves much more than hot. Lime-water is colorless, 
of a partially caustic taste, neutralizes acids perfectly, re- 
storing to reddened litmus its blue color. It is used as a 
test for carbonic acid, with which it gives the white car- 


What is the color it communicates to flame? What are the mineralog- 
ical names of the carbonate and sulphate of strontia? What is lime? 
Under what forms does it occurin nature? From the carbonate, how may 
lime be produced? What is the action of water on it? What are the 
properties of lime-water ? 


268 COMPOUNDS OF CALCIUM. 


bonate of lime. Cream of lime is nothing but lime-water 
in which hydrate of lime is mechanically suspended. The 
hardening of lime mortars depends chiefly on the absorp- 
tion of carbonic acid. Hydraulic lime possesses the qual- 
ity of setting under water. It contains oxide of iron, 
alumina, and silica. 

Lime is best detected by oxalate of ammonia, with 
which it gives a white precipitate of oxalate of lime, pro- 
vided the solution be not acid. 

Among other compounds of calcium may be mentioned 


Chloride of Calcium, CaCl=55'97, 


formed by dissolving carbonate of lime in hydrochloric 
acid, evaporating the solution to a sirup, and, on cooling, 
the chloride crystallizes. It is exceedingly deliquescent. 
Chloride of calcium, dried without crystallization, is used 
in organic analysis for collecting water, and, generally, in 
other chemical operations for drying gases. 


Fluoride of Calcium, CaF=39°24, 
called, also, fluor spar, and frequently found as a mineral 
associated with lead. Crystallizes in cubes, octahedrons, 
&c., of various colors. It is found in fossil, and, to a 
smaller extent, in recent bones. It is used for various or- 
namental purposes, and is the source from which the com- 
pounds of fluorine are derived. 


Sulphuret of Calcium, CaS=36°62. 


obtained by igniting the sulphate of lime with charcoal, 
and constitutes Canton’s phosphorus, commonly made by 
igniting oyster shells with sulphur ; possesses the curious 
quality of shining in the dark, after a brief exposure to 
the sun or to the rays of an electric spark. 


SALTS OF THE PROTOXIDE OF CALCIUM. 
Carbonate of Lime is abundantly found in nature, form- 
ing whole ranges of mountains, the limestones, marbles, 
&c., of mineralogists. It occurs pure in the form of Ice- 
land spar, in rhomboidal crystals, possessed of double re- 
fraction. It is dimorphous, assuming the form of six-sid- 
ed prisms, as in the mineral called Arragonite. It is an- 


What is milk of lime? For what purposes is the chloride of calcium 
used? Under what forms does fluoride of calcium occur? What singu- 
lar quality does the sulphuret of calcium possess? What are the dimor- 
phous forms of carbonate of lime? 


MAGNESIUM. 269 


hydrous, insoluble in water, but in water charged with 
carbonic acid it is soluble, and is deposited from such a 
liquid on boiling, or by the diffusion of carbonic acid into 
the air. The carbonic acid is expelled from this salt by 
a red heat, and the action of the more powerful acids, 
Carbonate of lime may be obtained in union with water, 
by boiling hydrate of lime with a solution of sugar. 

Sulphate of Lime—Gypsum—occurs native, both in 
crystals, the primary form being a rhombic prism, and also 
in extensive crystalline masses. It contains two atoms of 
water ; there is a variety, however, passing under the name 
of anhydrite, which contains no water. On calcining the 
hydrous sulphate of lime at a low red heat, it becomes plas- 
ter of Paris, and has the property of setting into a hard 
mass when made into a paste with water. The sulphate 
of lime is soluble in 500 parts of boiling water, and often 
occurs in the water of springs, to which it communicates 
hardness. 

Phosphate of Lime—Bone-earth Phosphate—is one of 
the tribasic phosphates ; it is precipitated when earth of 
bones is dissolved in muriatic acid, and the solution neu- 
tralized by ammonia. - 

Chloride of Lime—Bleaching Powder—is made by ex- 
posing hydrate of lime to chlorine. It is a white pow- 
der, exhaling a faint odor of chlorine, and is used exten- 
sively as a bleaching agent. 

MAGNESIUM. Mg = 127. 

Maenesium may be procured by igniting a mixture’ of 
chloride of magnesium and sodium in a porcelain cruci- 
ble; the chloride of sodium forms, and magnesium is set 
free. The chloride may be dissolved by water. 

It is a white, malleable metal, which melts at a red 
heat, and, with excess of air, oxydizes, forming 


Protoxide of Magnesium. MgO=20°713. 


This substance, called, also, calcined magnesia, or sim- 
ply magnesia, may be made by heating the carbonate to 
low redness ; the carbonic acid is driven off, and the mag- 
nesia remains as a white powder, insoluble in water, but 


Under what circumstances is it soluble in water? Under what forms 
does sulphate of lime occur, and for what purposes is it used? In what 
does the phosphate of lime occur? What is bleaching powder? How is 
magnesiumobtained? What are the properties of it? Under what names 
does the protoxide pass ? 

Z 2 


270 SALTS OF MAGNESIUM. 


neutralizing acids completely, and forming with them a 
complete series of salts. 

Magnesia occurs very abundantly in nature, often asso- 
ciated as a carbonate with carbonate of lime, as in dolo- 
mitic limestone. It also occurs in fertile soils, and is es- 
sential to the growth of certain plants. 

It is well distinguished from all the foregoing alkaline 
earths by the relation of its sulphate. The sulphates of 
baryta, strontia, and lime form a series of salts, the solu- 
bility of which, in water, is constantly increasing; to 
these the corresponding magnesia salt may be added ; it 
is very soluble. 

Magnesia is precipitated from its sulphate by the caus- 
tic alkalies, and by the carbonates of potash and soda as 
a carbonate, but not by the carbonate of ammonia in the 
cold. It may be detected by adding carbonate of ammo- 
nia and phosphate of soda in succession, when the phos- 
phate of magnesia and ammonia is precipitated. Heated 
before the blow-pipe, after having been moistened with 
nitrate of cobalt, magnesia becomes of a pinkish color. 


SALTS OF THE PROTOXIDE OF MAGNESIUM. 

Carbonate of Magnesia is found native, and may be 
prepared by boiling the sulphate with an alkaline carbon- 
ate, diffusing the precipitate in water, and passing a 
stream of carbonic acid through it; by spontaneous evap- 
oration the carbonate of magnesia is deposited in crystals. 
The carbonate of magnesia, the magnesia alba of the 
shops, is prepared by precipitating the sulphate of mag- 
nesia with the carbonate of potash; it occurs in light 
white cubical cakes, or in powder, and is not a true car- 
bonate, for it does not contain a full equivalent of carbonic 
acid. It is said to be a compound of one atom of hydrate 
of magnesia with three atoms of hydrated carbonate of 
magnesia. It is very slightly soluble in water. 

Sulphate of Magnesita—Epsom Salts of commerce—is 
produced by the action of dilute sulphuric acid on magne- 
sian limestone. Its crystals are small four-sided prisms, 
soluble in an equal weight of cold and three fourths their 
weight of boiling water, the solution having a bitter taste. 
A low heat expels six out of the seven equivalents of the 
combined water. 


What is dolomitic limestone? How may magnesia be detected? How 
is its carbonate prepared? Of what is Epsom salt composed ? 


ALUMINUM. 271 


Phosphate of Magnesia and Ammonia, one of the vari- 
eties of urinary calculus, may be formed artificially when 
a tribasic phosphate, a salt of ammonia, and a salt of mag- 
nesia are mixed together. 

Magnesium is the last of the alkaline earthy metals. Its 
history completes that of our first group of metallic bodies. 
At the head of the second group we find aluminum, the - 
first of the earthy metals. 


ALUMINUM. Al=13°7. 

Obtained, by Wholer, by the action of sodium on the 
chloride of aluminum, being the same process as that 
given for the preceding metal. 

It is a gray powder, which melts beneath a red heat ; 
takes fire when heated in air, producing 


Sesquioxide of Aluminum. Al,O;=51°539. 


This oxide, called, also, alumina and clay, occurs nat- 
urally under certain forms, which are highly prized, as the 
ruby and sapphire. In a more impure condition it yields 
the various common clays, which also contain silica or 
metallic oxides, or other extraneous bodies. 

Alumina may be prepared from the sulphate of alumina 
and potassa, common alum, by precipitating the sulphuric 
acid by chloride of barium. The sulphate of baryta goes 
down, and there is left in the solution chloride of po- 
tassium and chloride of aluminum. When the mass is 
dried, water is decomposed ; hydrochloric acid is then ex- 
pelled, and alumina, mixed with the chloride of potassium, 
remains behind; the latter is to be dissolved away by wa- 
ter, leaving the alumina as a white substance, which, with 
water, forms a plastic mass, capable of being moulded, 
and retaining its shape when baked. After ignition, it 
adheres to the tongue, and during the act of drying it con- 
tracts considerably in volume, a property which formerly 
gave rise to the invention of Wedgewood’s pyrometer. 

The presence of alumina gives to the clays those prop- 
- erties which fit them for the purpose of the potter and 
brickmaker. Aluminais also used as a mordant to fix the 
colors of certain dyes upon cloth. 


In what form is the phosphate of magnesia and ammonia sometimes 
found? How is aluminum prepared? What is the constitution of its ox- 
ide? Under what natural forms does it occur? How may alumina be 

repared? What principle is involved in Wedgewood’s pyrometer? 
hat is meant by a mordant ? 


272 PORCELAIN.—EARTHEN-WARE.—GLASS. 


Alumina is precipitated from its solutions by fixed al- 
kalies, which yield a white hydrate of alumina, soluble in 
an excess of the precipitant. It is also thrown down by 
alkaline carbonates; and, when these precipitations are 
made in a solution tinged with coloring matter, the alu- 
mina carries it down with it. Such colored precipitates 
pass under the name of lakes; and it is this property of 
attaching such colors to itself, enabling it to cause their 
firm adhesion to cloth fibre, which is the principle of its 
application as a mordant. 

Among the purposes to which alumina is applied may 
be mentioned the manufacture of PorceLai, and the dif- 
ferent kinds of earthen-ware. The former substance, first 
made by the Chinese, is very compact and translucent. 
It consists essentially of clay mixed with a fusible body, 
which binds all its parts together, and is covered with a 
glaze, which does not terminate abruptly on the surface, 
but pervades the substance of the mass. In this respect 
it differs from common earthen-ware. Feldspar, or the 
silicate of lime, are bodies suitable for communicating this 
glassy structure. 

In the manufacture of porcelain, great care is taken to 
select clay free from iron. It is mixed with powdered 
quartz and feldspar, and the requisite shape given it either 
by the potter’s wheel, or by pressing it into moulds. It 
is then dried in the air, and more perfectly in a furnace, 
and, when ignited, forms dzscuzt. ‘This is dipped in the 
glaze, suspended in water, and becomes covered over with 
a uniform coat of it. It now remains to dry it once more, 
and fuse the glaze upon it. 

E:ARTHEN-WARE consists of a white clay mixed with sil- 
ica. It is glazed with a fusible material containing oxide 
of lead, and colored of different tints by metallic oxides ; 
for example, blue by cobalt. 

Connected with the manufacture of pottery, may also 
be mentioned the manufacture of Guass, of which there 
are several varieties, some consisting of silica, potash or 
soda, and lime, others containing a large quantity of oxide” 
of lead. If silica be heated with carbonate of potash and 
lime, or oxide of lead, carbonic acid is expelled, and glass 


How may the presence of alumina be recognized? What are lakes? 
What substances are used in the preparation of porcelain and earthen: 
ware? How is glass made ? 


SALTS OF ALUMINUM. ae is 


forms. The mass is kept in a fused condition till it is free 
from air bubbles, and is then cooled until it becomes plas- 
tic, so that it may be blown or moulded. 

Articles of glass, after they are manufactured, require 
to be annealed or slowly cooled down. ‘This allows their 
parts to assume a regular structure, and prevents excess- 
ive brittleness. 

Soluble glass is formed when silica is heated with twice 
its weight of carbonate of soda or potash. It derives its 
name from the fact that it is for the most part soluble in 
water. 

SALTS OF THE SESQUIOXIDE OF ALUMINUM. 

Sulphate of Alumina is made by dissolving alumina in 
dilute sulphuric acid. It enters into the composition of 
the alums. 

Sulphate of Alumina and Potash—Alum.—T his import- 
ant salt is prepared from alum slate. It crystallizes in 
octahedrons, has an astringent taste, reddens litmus paper. 
It dissolves in about eighteen times its weight of cold, and 
less than its own weight of boiling water. It contains 
twenty-four atoms of water, and, when exposed to heat, 
foams up, melting in its own water, which, being evapo- 
rated away, leaves a white porous mass, commonly called 
burnt alum. 

In the same way that the sulphate of potash unites with 
the sulphate of alumina, so, also, do the sulphates of am- 
monia and of soda, forming respectively the ammoniacal 
and soda alums. ‘The alumina in the common alum may 
be replaced, also, by the sesquioxides of iron, manganese, 
or chromium, giving iron, manganese, and chrome alums. 

The following metals, GLucinum, THortum, YTTRIvum, 
ZIRCONIUM, LANTHANIUM, and CrriuM, are very rare bod- 
ies, and, being of little interest, may be passed over with- 
out farther notice. 


Why must it be annealed? What are the properties of the sulphate 
of alumina and potash ? 


274 MANGANESE. 


LECTURE LX. 


Maneaneskt.—Its Seven Oxides—The Peroxide and its 
Applications.— Mineral Chameleon.— Acids of Manga- 
nese.—NSalts of the Protoxide.—Iron.—TIts Natural 
Forms.— Reduction on the Great Scale-—Cast Iron.— 
Wrought Iron —Steel.— Passive Iron. 

MANGANESE. Mn=e277. 
MANGANESE may be procured by igniting its oxides with 

a mixture of lampblack and oil in a powerful furnace, the 

reduction being somewhat difficult. It is a white metal, 

specific gravity 8013, requiring a white heat for its fusion, 
and oxydizing readily in the air. It is remarkable for the 
number of oxygen compounds which it yields; they are 
MnO SraiinsO, <3.VMaO0, « 2a Mn Owl. Os «+0 
MnO, «+ Mn,0,; 


designated respectively, 


Protoxide of manganese. Permanganic acid. 
Sesquioxide of manganese. Red oxide of manganese. 
Peroxide of manganese. Varvicite. 


Manganic acid. 

Of these, the protoxide may be made by passing hydro- 
gen gas over red-hot peroxide of manganese. It is of a 
green color, is a basic body, and forms a series of salts, of 
which the sulphate i is used in dyeing. It is isomorphous 
with magnesia and zinc. Hydrosulphuret of ammonia 
yields with it a flesh-colored precipitate, ferrocyanide of 
potassium a white, and the chloride of soda a dark brown 
hydrated peroxide. The sesquioxide is made by igniting 
the peroxide, as will be presently explained. The red 
oxide and varvicite occur as minerals; but of the whole 
series the peroxide is by far the most valuable. 


Peroxide of Manganese, MnO,—43°726, 
is found abundantly as a mineral, and passes in commerce 
under the name of black oxide of manganese, a name in- 
dicating its color. It is insoluble in water, and when ex- 
posed to a red heat gives off one fourth of its oxygen, 
forming the sesquioxide, as stated above, the action being 


How may manganese be obtained? What are its properties? How 
many oxides does it furnish? How may manganese be detected? What 
is the constitution of the peroxide ? 


COMPOUNDS OF MANGANESE. 275 


2(MnO,)... =... MnO; + O. 


On this fact is founded one of the processes for obtaining 
oxygen gas. Heated with hydrochloric acid, it yields 
chlorine, as has been explained. It was formerly called 
glassmakers’ soap, from the circumstance that it removes, 
when added to melted glass, the stain of protoxide of 
iron, by turning it into peroxide, and causes the glass to 
become colorless; but if too great a proportion of per- 
oxide of manganese is used, the glass assumes an ame- 
thystine color. 

Peroxide of manganese, when ignited with caustic pot- 
ash in a platina crucible, yields a substance known as 
Mineral Chameleon, which is of a green color. Water 
dissolves from it the Manganate of Potash, which is of 
a beautiful grass green, the solution speedily passing 
through a variety of shades of purples, blues, and reds. 
As yet, manganic acid is a hypothetical compound, and 
has not been insulated. When mineral chameleon is 
dissolved in hot water, a red solution is obtained of the 
Permanganate of Potash ; from the permanganate of ba- 
ryta a crimson solution of Permanganic Acid may be pro- 
cured by the aid of sulphuric acid ; but permanganic acid 
can not be obtained in the solid form. 

Among other compounds of manganese, the following 
may be named: 


Protochloride of manganese MnCl = 63°15. 
Perchloride “ is Mnz Clr = 303°19. 
Perfluoride “ * Mn2F'ly = 186°46. 


The protochloride may be made by acting on the per- 
oxide with muriatic acid, evaporating to dryness, and 
fusing at a red heat. Ondigesting with water, the proto- 
chloride dissolves, and any impurity of iron is left in the 
state of oxide. Then, by crystallizing, the chloride can 
be obtained in pink crystals. The perchloride is pro- 
duced when permanganate of potash, common salt, and 
sulphuric acid are heated. It is a dark greenish and 
volatile liquid. The perfluoride is obtained by distilling 
sulphuric acid, permanganate of potash, and fluor spar; 
it is a greenish yellow gas. 


What color does it give to glass? How is mineral chameleon made? 
What are its properties? Can manganic acid be insulated? How may 
the chlorides of manganese be formed? What are the properties of the 
fluoride ? 


276 IRON. 


SALTS OF THE PROTOXIDE OF MANGANESE, : 
Protosulphate of Manganese, formed by dissolving pro- 
toxide of manganese in sulphuric acid. ‘The fizure of its 
crystals depends on the temperature at which they were 
formed. ‘They have a rose-colored tint. It is insoluble 
in alcohol, very soluble in water, and is used by the dyers 
to produce a fine brown color. 

There is but one sulphuret of manganese. It is ob- 
tained as a hydrate when manganese is precipitated by 
hydrosulphuret of ammonia (Mn, HO). It is of a flesh- 
red color. 


IRON. Fe= 28°00. 

Iron sometimes occurs in a native state and as mete- 
oric iron, also as oxide, carbonate, sulphuret, &c. It is 
one of the most abundant of the metals. Much of what 
is found in commerce is derived from clay iron-stone, 
which is an impure carbonate containing silica, alumina, 
magnesia, and other foreign substances. The native per- 
oxide of iron, red hematite ; the hydrated peroxide, 
brown hematite; the black oxide, or magnetic iron ore, 
furnish some of chs finer varieties of the metal. 

From clay iron-stone metallic iron is procured by the 
action of carbonaceous matter and lime at a high temper- 
ature. The ore, having been roasted, is thrown into the 
furnace with coal and lime. Ifthe iron is in the ore asa 
silicate, the lime decomposes it at those high temperatures, 
forming a slag of silicate of lime, and the oxide of iron 
set free is instantly reduced by the carbonaceous matter ; 
the metal sinking down, protected by the slag, is let off 
by opening a hole in the bottom of the furnace. 

The substance thus produced is not pure iron; it con- 
tains carbon and other impurities, and passes under the 
name of cast or pig iron. It is purified by melting and 
sudden cooling, which converts it into fine metal ; this 
fine metal is then melted under exposure to air, which 
burns off the carbon as carbonic oxide, and the mass, 
from being perfectly fluid, becomes coherent. It is now 
subjected to violent mechanical action, such as hammer- 
ing or rolling; this forces out or burns off the impurities, 


What is the formation and use of the protosulphate of manganese ? 
What are the forms under which iron chiefly occurs? How is it obtain- 
ed from clay iron-stone? What is cast iron? By what processes is it 
converted into wrought iron ? ate atet he 


IRON. 277 


increases its tenacity, and it becomes the wrought iron of 
commerce. 

Cast Iron melts reacily at a bright red heat, and expands 
in solidifying . on this depends its valuable application for 
making castings. Kept under the surface of salt water for 
a length of time, cast iron becomes converted into a body 
somewhat like plumbago, due, probably, to the removal 
of the iron as a chloride; the carbon which is left behind is 
sometimes observed, as it dries, to become hot: a phenom- 
enon to be accounted for by its porous state. These facts 
have been frequently verified in the case of cannon which 
have lain for years at the bottom of the sea. ‘There are 
two forms of cast iron, white and gray; the former con- 
tains about five per cent. of carbon, the latter three or four. 

Pure Iron may be obtained by decomposing precipitated 
peroxide of-iron by hydrogen gas, and melting the result. 
The metal has a bluish color, is more ductile than mallea- 
ble, and is the most tenacious of all bodies. It becomes very 
soft at a red heat, and possesses the welding property ; on 
this depends the art of forging it. Its specific gravity is 
77. Itis one of the few magnetic bodies, and, when soft, 
its magnetism is so transient that it may gain and lose that 
quality a thousand times in a minute. The melting point 
of iron is very high. In the mode of preparing it from 
cast iron it does not undergo the process of fusion, but its 
particles are simply welded together. The fibrous struc- 
ture which wrought iron possesses is the chief cause of its 
great tenacity; a wire 5th of an inch in diameter will 
bear a weight of 60 pounds. 

Steel, which is a valuable preparation of iron, is made 
by placing alternate strata of iron bars and charcoal pow- 
der in a close box and keeping them red hot. The pro- 
cess is known by the name of cementation. The iron 
gains about 1°5 per cent. of carson. Steel is much more 
fusible than iron, and becomes excessively hard and brit- 
tle by being brought to a red heat and then suddenly 
quenched in cold water. When allowed to cool slowly, it 
is quite soft, and various legrees of elasticity and hard- 
ness may be given to it by the process of tempering. 

By placing a piece of platina in nitric acid of a specific 


What are the properties of cast iron? What changes does it undergo 
under water? How may pure iron be obtained? What are its proper- 
ties? What is steel? How is it made, and what are its properties ? 


AaA 


~ 


278 OXIDES OF IRON. 


gravity of 1°34, and then bringing an iron wire in contact 
with it and withdrawing the platina, the iron assumes a 
passive or allotropic state. It now exhibits no tendency 
to unite with oxygen, cannot precipitate copper from its 
solutions, and simulates the properties of platina and gold. 


LECTURE LXI. 


Tron.— Oxides of— Three Oxides and Ferric Acid.— Tests 
for Iron.—Salts of the Protoxide and Peroxide.— The 
Sulphurets.—NickeL.—Its Reduction from the Oxalate. 
— Coxsa.t. — Smalt. — Zaffre. — Sympathetic Ink. — 
Zinc.— Distillation of —Salts of the Protoxide. 


IRON AND OXYGEN. 

Iron burns with rapidity in oxygen gas, as may be 
Fig.963. proved by igniting a piece of it in wire coiled 
into a spiral form in a jar of that gas (Ig. 263), 
when it will be found to take fire and burn beau- 
tifully. In atmospheric air, under favorable cir- 
cumstances, the combustibility of this metal may 
be proved. Thus, fine iron filings, sprinkled in 
the flame of a spirit lamp, burn with scintilla- 
tions; exposed to air and moisture, it slowly 
rusts. Iron yields four oxides : 


Protoxides . ".2. «FeO. ==)-36013. 
Black oxide. . . . Fe;,O, =116°052. 
Peroxide .%. . . FegOy== 80°039. 
Ferric acid .-¢ ..dfeO3 == 52:039. 


Protoxide of Iron. FeO=36:013. 


This oxide has not yet been insulated, but it exists, 
united with acids, in an extensive series of salts, from 
which it is thrown down as a hydrate by alkalies, and is 
then of a white color, which darkens as it passes into the 
state of peroxide. Ferrocyanide of potassium gives a 
white precipitate, and the ferridcyanide a deep blue. Hy- 
drosulphuret of ammonia gives a black sulphuret of iron. 
Sulphureted hydrogen and gallic acid give no precipitate. 


How may iron be rendered passive? How may the rapid oxydation of 
iron be illustrated? How many oxides does this metal yield? What 
are the reactions which the protoxide furnishes with tests ? 


OXIDES OF IRON. 279 


Black Oxide of Iron. Fe;0,=116°0852. 


This oxide, known also as the magnet or loadstone, is 
found as a mineral. It is a compound of the protoxide 
and peroxide. The scales of iron found in blacksmiths’ 
forges mainly consist of it. It may also be produced by 
decomposing the vapor of water by metallic iron in a red- 
hot tube. 


Peroxide of Iron, Fe,0;=80-039, 


is found in nature as oligist iron, or as a hydrate. Itmay 
be produced artificially as a hydrate by precipitation from 
a solution of persulphate of iron by a caustic or carbona- 
ted alkali, or in a pure state by igniting green vitriol; 
there is then left a red powder, known as rouge, used for 
polishing metals. This oxide is not magnetic; it is the 
basis of a series of salts which yield, with alkalies, a brown 
hydrated peroxide; with ferrocyanide of potassium, Prus- 
sian blue; with sulphocyanide of potassium, a blood-red 
solution; with tannin and gallic acid, a black. This last 
is of considerable interest, constituting the basis of ordi- 
nary ink. 

The presence WR iron can always be determined by 
passing it into the condition of peroxide, and applying the 
foregoing tests. 


Ferric Acid, FeO,;=52:039, 


is prepared by heating peroxide of iron with four parts of 
nitrate of potash. The result is treated with cold water, 
which yields a red solution of the ferrate of potash. This 
slowly decomposes in the cold, and very rapidly when the 
solution is warm. ‘The ferrate of baryta precipitates 
when the potash solution is acted on by a soluble salt of 
baryta. It is a permanent body, of a crimson color. 

Among other compounds of iron, the following may be 
named : 


Protochloride of iron ... . %1«. « eC? +=: 63°47. 
Perchloride “ oN pew ow eee Orbs aa tO oez 
Protiodide s wee citi ai) ee Date eo oe. 
Protosulphuret “ OY IS Ot Oi ie ae Se 
Sesquisulphuret “ ee ies eee) eeOa yt a LOL 
Bisulphuret by ot speeeentl sia Cave n GOSS. 


Under what natural forms does the black oxide occur? How may it be 
formed artificially ? What are the natural forms of the peroxide? How 
may it be prepared? For what purposes is itused? What is its action 
with reagents? What is common ink? How may the presence of iron 
be detected? What are the properties of ferric acid? Of the other com- 
pounds, mention some of interest. 


“nt 


Any 


280 SALTS OF IRON. 


Of these, the protochloride is formed by passing hydro- 
chloric acid over red-hot iron. It is white, but forms a 
green solution in water. The perchloride, in solution, by 
dissolving peroxide of iron in hydrochloric acid. The 
protiodide, by boiling an excess of iron filings with iodine, 
and evaporating; it forms, on cooling, a dark gray mass. 
Its solution absorbs oxygen from the air. The protosul- 
phuret of iron, which is much used for forming sulphuret- 
ed hydrogen, may be made by heating a mass of iron to 
a white heat, and applying to it roll sulphur, and receiv- 
ing the melted globules in a bucket of water. It may 
also be procured by igniting iron filings with sulphur. 
The bisulphuret occurs abundantly as a mineral of a gold- 
en yellow color, crystallized in cubes or allied forms, and 
knownas Iron Pyrites. It frequently assumes the form of 
various organic remains, being one of the common petri- 
fying agents, but in this state differs essentially from the 
cubic pyrites, both in color and oxydizability, these fossil 
remains rapidly decaying under exposure to the air, but 
the other form being unacted on. Besides these, there is 
a sulphuret of iron which is magnetic. 


SALTS OF THE PROTOXIDE OF IRON. 
Carbonate of Iron may be obtained from the sulphate 
by an alkaline carbonate, falling as a whitish precipitate. 
It turns brown, however, from the absorption of oxygen. 
It occurs as a mineral in spathic iron, and dissolves in 
water containing carbonic acid, forming chalybeate waters. 
Protosulphate of Iron—Copperas—Green Vitriol—is 
prepared largely by the oxydation of iron pyrites, and 
crystallizes in oblique prisms of a grass green color. It 
has a styptic taste, dissolves in twice its weight of cold, 
and three fourths its weight of boiling water. It contains 
five atoms of water. At a low red heat it becomes anhy- 
drous. In this state it is used for the manufacture of the 
Nordhausen sulphuric acid. 
SALTS OF THE PEROXIDE OF IRON. 
Persulphate of Iron may be formed by adding to a so- 
lution of the protosulphate of iron half an equivalent of 
sulphuric acid, and peroxydizing by nitric acid. With 
water it forms a red solution. 


~ “What is iron pyrites? What is the difference of its forms? How is 
the carbonate of iron formed? Whatis the process for preparing the sul- 
phate? How is the persulphate obtained? 


NICKEL AND COBALT. 281 


NICKEL. Nz = 29°5. ’ 

NickEL may be obtained by igniting its oxalate in a coy- 
ered crucible, carbonic acid escaping, and the metal being 
reduced. 

MO+C,0;...=...N+2(CO,); 
one atom of the oxalate of nickel yielding one of the met- 
al and two of carbonic acid gas. 

Nickel is a white metal, requiring a high temperature 
for fusion. It is magnetic, and has a specific gravity of 
8:5. It is commonly associated with iron in meteorites, 
and enters into the composition of German silver ; unites 
with oxygen, forming a protoxide and sesquioxide, the 
former yielding salts of a green color; the latter is an in 
different body. 


SALTS OF THH PROTOXIDE OF NICKEL. 

Sulphate of Nickel crystallizes from its solutions witk 
six atoms of water in slender green prisms, which, wher 
exposed to the sun, change into an aggregate of octahe 
drons, becoming opaque. 

Nickel is chiefly used in the preparation of German 
silver, an alloy of copper, zinc, and nickel. It is of a 
white color, takes a good polish, and is malleable. 

: COBALT, Co = 29'5, 

is generally associated with iron and nickel, and with 
them occurs in meteoric iron. Like the preceding metal, 
it may be obtained by igniting its oxalate in a covered 
crucible, carbonic acid being disengaged and metallic 
cobalt left. It is a pinkish white metal, requiring a high 
temperature for fusion. Its specific gravity is 7°8. It is 
magnetic, as recent experiments have proved. It forms 
a protoxide and a sesquioxide, the former being the basis 
of a class of salts which are chiefly of a pink or blue col- 
or. Smalt is a silicate of cobalt, and Zaffre an impure 
oxide ; the former is used to communicate to paper a faint 
blue tinge, and the blue color which the oxide gives to 
glass is taken advantage of in coloring the common vari- 
eties of earthen-ware. Cobalt is easily detected upon this 
principle. 


By what process is nickel obtained? What are its properties? Under 
what remarkable circumstances does it occur with iron? What change 
does the sulphate of nickel undergo in the sunlight? How is cobalt pro- 
cured? Is it magnetic like nickel? What is smalt? What is zaftre ? 
What are the uses of cobalt? 


Aa2 


282 ZINC. 


The chloride of cobalt may be made by dissolving the 
oxide or the metal in hydrochloric acid. It is a pink 
solution, which turns blue when dried. It forms a beau- 
tiful sympathetic ink, for letters written with it, especially 
on paper which has a pinkish tinge, are entirely invisible, 
but become of a bright blue color when the paper is 
warmed, the letters again fading as they become cool and 
moist. 


ZINC. Zn = 323. 
ZINC is a very abundant metal, immense quantities of 
it occurring in the state of New Jersey and in various 

Fig. 964, Other places. From zinc blende, which is a sul- 
, phuret, converted by roasting into an oxide, or 
| from the carbonate brought into the same state 
| by ignition, the metal may be obtained by the 
process of distillation by descent. The ox- 
ide, mixed with charcoal, is introduced into a 
crucible which has an iron tube passing through 
a hole in its bottom, as seen in Fig. 264, and 
the lid being luted on, the temperature is raised 
to a white heat, and the zinc, distilling over, 
may be condensed in water. 

Zinc is a bluish-white metal, which melts at about 770° 
F., and, if exposed at a bright red heat to the air, takes 
fire and burns with a brilliant pale green flame. Its spe- 
cific gravity is about 7-00. At common temperatures it is 
brittle, but it may be rolled into thin sheets at about 300° 
F., and then retains its malleability when cold. During 
its combustion there arises from it a great quantity of 
flocculent oxide, which formerly went under the name 
of nthil album, or philosopher’s wool. Among the com- 
pounds of zinc may be mentioned 


Protoxide of zinc. .420% |) ..Z2nO =40°313: 
Chloride wv hes BPA OT = Sey 
Sulphuret <t ope e is ee eS ee 


Of these, the oxide is formed, as has been said, during 
the combustion of zinc. It is also precipitated as a white 
hydrate from its soluble salts by potash or soda, soluble 
in excess of the precipitant. The chloride may be made 
by the action of hydrochloric acid on metallic zinc. It is 


What property does the chloride possess? By what process is zine ob- 
tained? Is there any connection between its ductility and temperature ? 
During combustion, what arises from it? How may it be detected? 


CADMIUM.—TIN. 283 


used in the arts for soldering under the name of butter of 
zinc. The sulphuret occurs as a mineral under the name 
of zinc blende. 


SALTS OF THE PROTOXIDE OF ZINC. 

Sulphate of Zinc— White Vitriol—This salt is formed 
in the process for procuring hydrogen gas by the action 
of dilute sulphuric acid on zinc. It crystallizes in color- 
less prisms with six atoms of water, and is soluble in two 
and a half parts of cold water. It has a styptic taste, 
and reddens vegetable blues. There are three different 
subsulphates of this oxide. 

Silicate of Zinc, the electric calamine of mineralogists ; 
remarkable for becoming electric when heated. 


LECTURE LXII. 


Capmium.—Sources of.—Its Volatility —T1n.— Block and 
Grain.—Its Properties —Protoxide and Stannic Acid.— 
Chlorides of Tin.— Mosaic Gold.— Its Uses—Curo- 
mium. — Chromiron.— Green Oxide and its Uses.— 
Chromic Acid.— Salts of the Sesquioxide.— Salis of 
Chromic Acid — Other Metals —Titanium. 

CADMIUM. Cd = 55°8. 

Capmium usually occurs associated with zinc as a car- 
bonate. In the preparation of that metal by distillation, 
as has been described, the cadmium first comes over. 
From any impurity of zinc it may be separated by pre- 
cipitation from an acid solution by sulphureted hydrogen, 
which throws the cadmium down as a yellow powder, 
put does not act onthe zinc. The sulphuret of cadmium 
is then dissolved in nitric acid, the oxide precipitated by 
potash, and, when dry, reduced by charcoal. The com- 
pounds of cadmium are not important. The metal itself 
is very volatile. 

TIN. Sn = 57°9. 

Tin occurs as an oxide in England, Mexico, Germany, 
and the Hast Indies. It may be reduced by the action 
of charcoal at a high temperature. It is found in com- 


How is white vitriol prepared? What is electric calamine? Under 
what circumstances does cadmium occur? What are the native forms of 
tin? 


284 : COMPOUNDS OF TIN. 


merce under two forms, block tin and grain tin, Ifa bar 
of tin is heated, the purer parts, being the more fusible, 
ooze out of it, constituting grain tin, and the mass which 
is left behind is block tin. ; 

Tin is a white metal like silver. It oxydizes in the air 
superficially, the action ceasing as soon as a thin crust is 
formed. At a red heat it oxydizes rapidly, forming putty 
powder, used for polishing metals. It is very malleable, 
and may be rolled into thin foil. When bent backward 
and forward it emits a crackling sound. It is very soft; 
its specific gravity 7°2. It melts at 442°, and burns when 
raised to a high temperature in the air. Some of its com- 
pounds are 


Provoxide Of tin a. ee cs DE OO SL, 
Gesquioxide Ve." ea Rg Op 129 S39 
Peroxide Wis 2a. CLS SHO pt HI8 SE; 
Protochioride sn Saws ben sw ROL =e 93314 
Perchlorid@ )- a toons ue 4a ele ee pee 
Protosulphuret’ . 2... . . SaS-> = 74: 

Persulphuret .. 3).. «s SnS_ = 90°. 


The protoxide may be made by precipitation from the 
protochloride by carbonate of potash. Itis to be washed 
with warm water, and its water finally driven off in a cur- 
rent of carbonic acid gas at a red heat. It is of a black 
color, is easily set on fire in atmospheric air, passing into 
the condition of peroxide. Its salts reduce the noble 
metals to the metallic state, when added to their solutions, 
and yield with the chloride of gold the Purple of Cassius. 
The peroxide, called also stannic acid, from exhibiting 
weak acid properties, may be made by the action of ni- 
tric acid on tin. It is a hydrate in the form of a white 
powder, insoluble in acids and water; but if obtained by 
precipitation from perchloride of tin, it is soluble both in 
acids and alkalies. Melted with glass, it forms a white 
enamel. 

The protochloride may be made by dissolving tin in 
warm hydrochloric acid. The solution, when concentra- 
ted, deposits crystals of the hydrated protochloride. These 
are decomposed when heated. The anhydrous protochlo- 
ride may be had by passing hydrochloric acid gas over 
metallic tin at a red heat. The perchloride is procured 


What are block and graintin? What arethe properties of tin? When 
a bar of tin is bent backward and forward, what phenomenon arises ? 
How is the protoxide made, and how do its salts act on those of the noble 
metals? Howis stannic acid prepared? What does it yield with glass? 


CHROMIUM. 285 


by distilling eight parts of tin with twenty-four of corro- 
sive sublimate. It is a smoking fluid, and was formerly 
called the Fuming Liquor of Inbavius. A solution of 
this substance, much used in dyeing, is made by dissolving 
tin in nitromuriatic acid, or by warming a solution of the 
protochloride with a little nitric acid. 

Of the sulphurets, the first may be formed by pouring 
melted tin on sulphur, and igniting the powdered result 
with more sulphur in acrucible. It is a bluish gray com- 
pound. The persulphuret is obtained when two parts of 
peroxide of tin, two of snlphur, and one of sal ammoniac 
are ignited in a retort. It is a body of a golden yellow 
color, formerly called Aurum Musivum, or Mosaic gold, 
in small scales of a greasy feel, and is used for exciting 
electrical machines, being much more energetic than the 
common amalgam, though less durable in its power. 

Tin furnishes several valuable metallic combinations ; 
Tin Plate is sheet iron superficially alloyed with it. 
The soft solders are alloys of lead and tin. Pewter is an 
alloy with antimony. 


CHROMIUM. Cr=28. 

Curomium occurs abundantly near Baltimore as the 
chromate of iron (Chrome Iron), more rarely as the red chro- 
mate of lead. The metal may be obtained by the action 
of charcoal on the oxide at a high temperature, and is of 
a yellowish-white color. It takes its name from its tend- 
ency to produce highly colored compounds. It is very 
infusible, and has a specific gravity of about 6-00. Its com- 
pounds, to be here described, are 


Sesquioxide of chromium . . . . Cr,O3;= 80°039: 
Chromic acid“. 3. wk ws GPO == 58-089: 
Sesquichloride of chromium . . . Cr,O 3 = 162°26. 


The sesquioxide may be prepared by heating the chro- 
mate of mercury to redness in a crucible. The mercury 
is driven off, and the chromic acid partially deoxydized, 
leaving a beautiful grass-green powder, the sesquioxide. 
It may also be obtained by heating the bichromate of pot- 
ash red hot, and washing the residue in water; also as a 
hydrate, by boiling a solution of bichromate of potash with 


What is the fuming liquor of Libavius? How is mosaic gold made, 
and what is its use? What alloys does tin furnish? Under what forms 
does chromium occur in nature? How is its sesquioxide prepared, and 
what is its use? 


286 COMPOUNDS OF CHROMIUM. 


muriatic acid, and adding alcohol; the mixture becomes 
of a green color, and ammonia precipitates the hydrated 
sesquioxide. It is a weak base, yielding a class of salts 
of a blue or green color. In the state of hydrate it is sol- 
uble in acids ; but, on making it red hot, it suddenly be- 
comes incandescent, passes into another allotropic state, 
and is now insoluble. This sesquioxide is isomorphous 
with the sesquioxides of iron and alumina. In its two al- 
lotropic states, it yields corresponding classes of salts, one 
of which is green, and the other reddish green. It is used 
for communicating a green color to porcelain. 

Chromic Acid may be made by adding one volume of a 
saturated solution of bichromate of potash to one anda 
half of oil of vitriol. On cooling, red crystals of chromic 
acid are deposited. It is isomorphous with sulphuric acid, 
produces with bases yellow and red salts, is a powerful 
oxydizing agent, is decomposed by a red heat into the ses- 
quioxide, destroys the color of indigo and other dyes, 
and may be detected by producing with the salts of lead, 
chrome yellow, and by its ready passage, under the influ- 
ence of deoxydizing agents, into the sesquioxide. 

The sesquichloride is procured when chlorine is passed 
over a mixture of the sesquioxide and charcoal in a red- 
hot tube. It is a lilac-colored body, which forms a green 
solution in water. ‘There is also an oxychloride, which 
may be distilled as a deep-red liquid from a mixture of 
chromate of potash, common salt, and oil of vitriol. The 
fluoride, which is a red gas, is obtained by distilling in a 
silver retort a mixture of chromate of lead, fluor spar, and 
oil of vitriol. It is decomposed by the moisture of the air, 
forming chromic and hydrofluoric acids. 


SALTS OF THE SESQUIOXIDE OF CHROMIUM. 

Sulphate of Chromium and Potash—Chrome Alum.— 
When the oxide of chromium is dissolved in sulphuric 
acid and mixed with the sulphate of potash and a little 
free sulphuric acid, crystals of chrome alum are deposit- 
ed in red or blue octahedrons. The sulphate of chromium 
alone does not crystallize. 

Chrome Iron, a compound of the sesquioxide of chro- 
mium and the protoxide of iron, is found native, crystal- 


are the chloride and fluoride obtained? What is the form of the latter 
body? What is chrome alum? 


SALTS OF CHROMIC ACID. 287 


lized in octahedrons, and alsomassive. It furnishes most 
of the compounds of chromium. 


SALTS OF CHROMIC ACID. 

Chromate of Potash may be made by igniting chrome iron 
with one fifth its weight of nitrate of potash. It crystal- 
lizes in small, lemon-yellow prisms, and is very soluble 
in hot water. The crystals are anhydrous. 

Bichromate of Potash may be prepared from the for- 
mer by adding an equivalent of acetic acid: it crystal- 
lizes in prisms of a ruby red. Large quantities are con- 
sumed by dyers. 

Chromate of Lead—Chrome Yellow, obtained by pre- 
cipitation from either of the foregoing salts by a soluble 
salt of lead. It is used as a paint. 

Dichromate of Lead is formed by adding chromate of 
lead to melted nitrate of potash, and dissolving out the 
chromate of potash and excess of nitre by water. It is of 
a beautiful red color. 

The following metals, Vanapium, Tunesten, Motys- 
DENUM, Osmium, and CoLuMBIUM, are not applied to any 
purposes in the arts, or are so rare as not to be of general 
interest. Trrantum might be included in the same obser- 
vation ; it is, however, deserving of remark as being a red 
metal like copper, and titanic acid, one of its oxygen com- 
pounds, is used in the coloring of artificial teeth. 


LECTURE LAXIII. 


ArsEnic.—Preparation of the Metal. Properties of Ar- 
senious Acid.—Two Varieties of it.— Two methods of 
detecting %t.—Process in Cases of Poisoning —Sulphur- 
eted Hydrogen Test—Marsh’s Test— The Copper Test. 
— Difficulties arising from Antimony. 

ARSENIC, As = 37-7. 
ARSENIC is obtained by sublimation in a current of air 
of the arseniuret of cobalt and iron, the vapor condensing 
as a white oxide. This being mixed with powdered char- 


What is the constitution of the two chromates of potash? What is 
chrome yellow? What is the color of titanium? From what substances, 
and in what manner, is arsenious acid prepared ? 


ae 


288 COMPOUNDS OF ARSENIC. 


. coal, or black flux, and heated, the metallic arse- 
nic sublimes. The process may be conducted in 
a tall vial imbedded in a crucible filled with sand, 
two thirds of the vial projecting above the heated 
sand. On this cooler portion the metal condenses. 
.# It is also sometimes found in a native state. 
Arsenic is a metallic body, of an aspect darker than cast 
iron ; it is very brittle, its specific gravity is 5°88, and, when 
slowly sublimed, it crystallizes in rhombohedrons. At 
356° F, it sublimes without undergoing fusion, its melting 
point being much higher than that of sublimation. _ Its va- 
por has a smell of garlic, as may be readily recognized by 
throwing a little arsenious acid on a red-hot coal. Arse- 
nic prepared by black flux tarnishes, it is said, from con- 
taining a little potassium. Among its compounds, the fol- 


lowing may be mentioned: 


Arseniots acid: | 6s 6. os) a As gO ==, 99°A39. 
Arsenic acid . . oe eo ASg On ae 115-465. 
Protosulphuret of arsenic ly dikes) giv GEES 7 Meee ees Oe 
Sesquisulphuret of arsenic . . . As,S3 ==123°7. 
Arseniureted hydrogen « . . 1. AsH = 38°7. 


Arsenious Acid is formed when arsenic is sublimed in 
atmospheric air. It is a white substance, which, when 
the process is conducted slowly, crystallizes in octahe- 
drons. Similar octahedral crystals may be obtained by 
heating arsenious acid itself in a tube to 380° F. When 
the operation has been recently performed and a large 
mass sublimed, it is a glassy, transparent body, which in 
the course of time slowly becomes milk-white. The spe- 
cific gravity of arsenious acid is 3°7. It is nearly taste- 
less, of sparing solubility in water, the two varieties dif- 
fering i in this respect. By 100 parts of water, 11°5 of the 
opaque, but only 9°7 of the transparent, are dissolved. 
This substance passes currently under the name of arse- 
nic. It ought not to be forgotten that the arsenic of chem- 
ical writers and that of commerce are very different bod- 
ies: the one is black and the other white; the one is a 
metal and the other its oxide. 

Arsenious acid may be detected by several methods. 


How is the metal obtained from it? What are its properties? What 
is the odor of its vapor? Why can not it be melted? From the metal, 
uow may arsenious acid be procured? What change does the glassy va- 
riety undergo in time? Of these varieties, which is most soluble in water ? 
What is the difference between the arsenic of chemists and the arsenic 


of commerce? 


2 


TESTS FOR ARSENIC. 289 


1st. With ammonia sulphate of copper, it gives an 
emerald green precipitate; the arsenite of copper, or 
Scheele’s green. 

2d. With the ammonia nitrate of silver, a canary yel- 
low precipitate ; the arsenite of silver. 

3d., With sulphureted hydrogen, a solution, previously 
acidulated with acetic or muriatic acid, yields a yellow pre- 
cipitate, the sesquisulphuret of srienie orpiment. ‘This, 
when dried and ignited with black flux (a mixture of 
charcoal and carbonate of potash, obtained by igniting 
cream of tartar in a covered crucible), yields a sublimate 
of metallic arsenic. 

4th. With the materials for generating hydrogen gas; 
that is, sulphuric acid, zinc, and water, placed in a bottle ; 
if arsenious acid be present, arseniureted hydrogen is dis- 
engaged. When set on fire, it burns with a pale blue 
flame, emitting a white smoke ; and if a piece of cold glass 
be held in the flame, there is deposited upon it a black 
spot of arsenic, surrounded by a white border of arsen- 
ious acid. This stain 1s volatilized on heating the glass. 
Or if the arseniureted hydrogen be conducted through a 
tube of Bohemian glass, made red hot at one point by a 
spirit lamp, it is decomposed, and metallic arsenic depos- 
ited on the cooler portions beyond the ignited space. 

5th. If a solution containing arsenious acid be acidu- 
lated with hydrochloric acid, and boiled with slips of cop- 
per, the metallic arsenic is deposited upon the copper as 

an iron gray crust. 

In cases of poisoning by this substance, it is unsatisfac- 
tory to apply, in the first instance, color-giving tests, such 
as the first, second, and third; as the liquid obtained from 
the stomach is itself highly colored and turbid. It is, 
therefore, desirable to examine that organ and its contents 
minutely, endeavoring to discover any white granules, or 
specks, which may be supposed to be arsenious acid, and 
if such are found, to examine them separately. 

The contents of the stomach, the larger pieces having 
been divided, are to be boiled in water, and strained 
through a linen cloth. A current of chlorine gas passed 


What is the action of ammonia sulphate of copper on arsenious acid ? 
‘What of the ammonia nitrate of silver? What of sulphureted hydrogen ? 
W hat is the process for detecting it by arseniureted hydrogen? What is 
that by copper? In cases of poisoning, why can not color tests be applied T 
How is the liquid obtained from the stomach to be clarified ? 


Bes 


290 MARSH’S TEST. 


through this liquid coagulates and separates much of the 
animal matter; or, what is more convenient, if the solu- 
tion be first acidulated with nitric acid, and then nitrate 
of silver be added, much of the animal matter may be re- 
moved. By the addition of a solution of common salt, the 
excess of the silver salt may be precipitated, and the 
liquor being filtered, is then fit for the third or fourth of 
the foregoing tests. 

In the application of sulphureted hydrogen, the liquor 
having been clarified as just stated, the gas is passed 
through it until it smells strongly. It is then to be boiled 
for a short time, to expel the excess of gas, and filtered. 
The yellow precipitate of sesquisulphuret of arsenic, or 
orpiment, which is collected, is to be thoroughly dried, 
and introduced, with twice its bulk of black flux, into the 

Fig. 266. bulb, a, of a tube, such as Fig. 266, made of 
hard glass. On the temperature being rais- 
ed by a lamp, metallic arsenic sublimes, 
forming an iron black ring round the part, 
b. By: cutting off the bulb of the tube and 
heating the black crust oradually, it slowly sublimes to- 
ward the colder part, producing a white deposit of ar- 
senious acid in octahedral crystals. 

In the application of Marsh’s test, the liquor, having 
been cleared either. by chlorine or by nitrate of silver, as 
above described, is to be introduced into a, bottle con- 
taining dilute sulphuric acid and zinc, a tube, bent as 

Fig. 267. represented in Fug. 267, ad, passing lat- 

Z b erally from the cork; arsemunreed hy- 

drogen now passes off, and may be set 

on fire as it escapes from the end of the 

tube, and examined by holding in the 

flame a piece of cold glass, 6. If no spot 
be produced, then the tube, which for this reason should 
be made of a hard glass not containing lead, is to be ignit- 
ed by a spirit lamp at the point c, and the gas will de- 
posit its arsenic a little beyond that point. In this man- 
ner, the tube being kept red hot for hours, the smallest 
quantity of arsenic may be discovered. 

If the liquor, notwithstanding the care taken to clear it, 


Describe the test by sulphureted hydrogen. Describe Marsh’s test. 
How may a small quantity of metal be separated from a large quantity of 
liquid by this test? ~ 


ARSENIC. 291 


froths when the hydrogen is disengaged, so as to inter- 
fere with the results by choking the tube, the gas is best 
collected under a jar at the pneumatic trough, and may be 
subsequently examined. 

The fifth test, by copper, may be sometimes advanta- 
geously applied to collect the arsenic from solutions; the 
crust upon the copper may be subsequently examined, ei- 
ther by sublimation or otherwise. 

It is to be remembered that antimony will yield results 
closely resembling those of arsenic by Marsh’s test; but 
on heating the glass plate on which the stain has been de- 
posited, if it be arsenic, it will totally volatilize away; but, 
if antimony, though the flame of a blow-pipe be thrown 
upon it, it will not disappear, but only gives rise to a yel- 
low oxide, which turns white on cooling. 

In medico-legal investigations, it should also be re- 
membered that, as sulphuric acid and zine of commerce 
sometimes contain arsenic, it is absolutely necessary that 
the specimens about to be used be critically examined 
themselves by being tried alone before the suspected so- 
lution is added. 


LECTURE LXIV. 


ArRsENIC.—Antiseptic Quality of Arsenious Acid.—Anti- 
dote for Poisoning.—Arsenic Acid.—Isomorphous with 
Phosphoric Acid.—Realgar and Orpiment.—Arseniuret- 
ed Hydrogen.— Antimony.— Reduction of.— Oxides, 
Chlorides, and Sulphurets of —Antimoniureted Hydro- 
gen.— Detection of Antimony —TE.LuRIuM.— URANIUM. 
—Coprrer.—Reduction of-—-Use of Oxide— Detection 
of —Salts of Protoxide. 


ARSENIoUS AcID possesses a remarkable antiseptic qual- 
ity, and hence often preserves the bodies of persons who 
have been poisoned by it. Advantage is also taken of this 
fact by the collectors of objects of natural history in pre- 
serving their specimens. 


— 


When the liquid froths, what course is to be pursued? Whenmay the 
test of copper be advantageously applied? What metal closely resembles 
arsenic in these respects? Why is it necessary to examine the sulphuric 
acid and zinc employed in these experiments? Does arsenious acid pos- 
sess an antiseptic quality ? z . 


—_—$_$—$ ee 


292 COMPOUNDS OF ARSENIC. 


The antidote for poisoning by arsenic is the hydrated 
sesquioxide of iron. It may be made by adding carbon- 
ate of soda to the muriate of iron. It should be given in 
the moist state, mixed with water. After being once 
dried, it loses much of its power. It produces an inert 
basic arsenite of the peroxide of iron. 

Arsenic Acid is found in nature in union with various 
bases. It may be made by acting on arsenious acid with 
nitric acid, with the addition of a little hydrochloric acid, 
and evaporating till the nitric acid is expelled. The re- 
sulting acid contains three atoms of water, and is isomor- 
phous with tribasic phosphoric acid. The arseniates yield, 
with nitrate of silver, a dark-red precipitate of the triba- 
sic arseniate of silver. ‘The monobasic and bibasic forms 
of the acid are not known. It should not be forgotten in 
medico-legal inquiries respecting arsenic, that the arse- 
niate of lime may naturally replace phosphate of lime in 
bone earth, and this acid substitute the phosphoric in other 
parts of the system. 

The protosulphuret of arsenic may be obtained by melt- 
ing arsenious acid with sulphur. It occurs as a mineral 
Realgar, and is a red-colored substance. 

The sesquisulphuret is deposited when a stream of sul- 
phureted hydrogen is passed through a solution of arse- 
nious acid. It is a yellow body, and is used in dyeing ; 
it is also known under the name of Orpiment. 

Arseniureted Hydrogen is prepared by acting on an al- 
loy of zinc and arsenic with dilute sulphuric acid. It is 
a colorless gas, burns with a blue flame, exhales an odor 
like garlic. Its specific gravity is 2695. It is decom- 
posed by chlorine, iodine, and the arsenic is separated by 
heat and by the rays of the sun. 


ANTIMONY. Sd =64°6. 

This metal occurs commonly as a sesquisulphuret in 
nature, from which it may be obtained by heating with 
iron filings, a sulphuret of iron forming, and metallic an- 
timony subsiding to the bottom of the crucible. It may 
also be obtained by fusing the sulphuret with black flux, 


What is the antidote for this poison? How is it prepared? How is 
arsenic acid prepared? What fact arises from the isomorphism of arsen- 
ic and phosphoric acids?) What is realgar? What is orpiment? How 
may arseniureted hydrogen be made ? ‘From what source is antimony ob- 
tained? What isthe process for its preparation? 


COMPOUNDS OF ANTIMONY. 293 


which produces a sulphuret of potassium and metallic 
antimony. 

Antimony is a blue-white metal, of a very crystalline 
structure, and so brittle that it may be pulverized. It 
melts at 810° F. Its specific gravity is 6°7. It possess- 
es, at high temperatures, an intense affinity for oxygen; a 
fragment of it the size of a pea being ignited on a piece 
of charcoal before the bl ow-pipe, and then suddenly thrown 
on the table, takes fire, breaking into a multitude of glob- 
ules, and filling the air with fumes of the white sesqui- 
oxide. Antimony yields the following compounds: 


Sesquioxide of antimony . . . . Sb,O3 = 153-239. 
PADEUOMIOUS OEIC! 1k koy oe cet ould Oakes ge O) aoe 
Antimonic acid . . 5A 6 SSO SS es 
Sesquichloride of antimony & eA SOSCE == 23546, 
Perchloride Be 6 ROE aR} 
Sesquisulphuret 4, Wa har] A Pi tly irs 
Persulphuret 4; shee Bn eh ee T, 
Oxysulphuret LY : 286, S; + Sb,03 = 5082. 


The Sesquroxide of Avance may be made by adding 
to an acid boiling solution of chloride of antimony car- 
bonate of soda. It is a gray powder, and is the base of a 
class of salts, among which tartar-emetic may be men- 
tioned. These salts give an orange-colored precipitate 
with sulphureted hydrogen. 

Antimonious Acid is produced by heating the oxide of 
antimony, or antimonic acid. It is a white powder, and 
unites with bases, forming antimonites. 

Antimonic Acid may be prepared by acting on metallic 
antimony with nitric acid. 

Sesquichloride of Antimony is made by dissolving one 
part of sulphuret of antimony in five of hydrochloric acid, 
and distilling. As soon as the matter which passes over 
becomes solid, the receiver is to be changed, and, contin- 
uing the heat, the sesquichloride is collected. It was for- 
merly known as butter of antimony. The perchloride 
may be made by burning antimony in chlorine gas. The 
oxychloride is produced when the sesquichloride is placed 
in contact with water. It was formerly known as pow- 
der of algaroth, 

The sesquisulphuret occurs abundantly as a mineral, as 


What are its properties? What color is the precipitate yielded by thse 
salts of the sesquioxide and sulphureted hydrogen? How is antimonious 
acid prepared? What is the butter of antimony? What is the powder 
of algaroth?) What is the aspect of the native sesquisulphuret ? 


BB. 


EE 


294 COMPOUNDS OF ANTIMONY. 


has been said. It is also formed by the action of sulphu- 
reted hydrogen on the salts of the oxide of antimony. In 
this case it is of an orange color, in the former it has a 
metallic aspect. The persulphuret is procured when the 
sesquisulphuret and sulphur are boiled in a solution of 
potash, the liquor filtered, and an acid added, a yellow 
precipitate going down. It was known formerly as the 
Golden Sulphuret of Antimony. ‘The oxysulphuret occurs 
native as the red ore of antimony, and may also be made 
by boiling the sesquisulphuret with a solution of potash. 
On cooling, precipitation of it takes place. It is stated, 
however, by Berzelius, that this is not a true compound, 
but merely a mechanical mixture of the oxide and sulphu- 
ret in irregular proportions. This precipitate is also known 
under the name of Kermes Mineral. rom the liquor, af- 
ter the kermes is separated, an acid throws down the gold- 
en sulphuret of antimony. 

Antimoniureted Hydrogen.—When hydrogen is evolved 
from a solution containing tartar emetic (tartrate of anti- 
mony and potash), this substance is produced. It isa gas, 
having a superficial resemblance to arseniureted hydro- 
gen, and when used as in Marsh’s apparatus, gives a stain 
un glass resembling that of arsenic. I*rom arsenic 1t may 
be distinguished by not being volatile. 

The soluble salts of antimony may be distinguished by 
giving an orange precipitate with sulphureted hydrogen, 
soluble in sulphuret of ammonium, but again precipitated - 
by an acid. 

Antimony furnishes some valuable alloys: printer’s 
type metal, for example, is an alloy of this substance with 
lead. It expands in the act of solidifying, and, therefore, 
takes accurate impressions of the interior of a mould. 


TELLURIUM. Ye=64°2. 

TELLURIUM is a rare metal, of a white color, very fusi- 
ble and volatile, having several analogies with selenium, 
and uniting with hydrogen to form tellureted hydrogen, 
which, with water, yields a claret-colored solution. 


Wi ANTUM Sois= 2175 
is likewise a very rare metal, of the nature of which there 


——— 


What is the golden sulphuret? What is Kermes mineral? How is 
antimoniureted hydrogen made? How may the salts of antimony be dis- 
tinguished? What are the properties of tellurium ? 


COPPER. 295 


are considerable doubts, it being supposed that what was 
formerly regarded as the metal 1s in reality its protoxide. 
It may be remarked, if these observations are incorrect, 
that uranium has the highest equivalent of any of the ele- 
mentary bodies. It is used to a small extent to give black 
and yellow colors to porcelain. , 


COPPER Cu=—se: 

Copper is often: found native, and in certain parts of the 
United States in masses of very great magnitude. It also 
occurs as a carbonate and sulphuret. In the latter com- 
bination, it is found with the sulphuret of iron, as yellow 
copper ore. This being roasted, the sulphuret of iron 
changes into oxide, the copper sulphuret remaining un- 
changed. The mass is then heated with sand, which 
yields a silicate of iron, the sulphuret of copper separa- 
ting. This process is repeated until all the iron is parted ; 
and now the sulphuret of copper begins to change into 
the oxide, which is finally decomposed by carbon at a high 
temperature. 

Copper is a red metal, requiring a high temperature for 
fusion. Its specific gravity is 8617. It has great tenac- 
ity, aud is ductile and malleable. A polished plate of 
it, heated, exhibits rainbow colors, and is finally coated 
with the black oxide. It is one of the best conductors of 
heat and electricity. Among its compounds, the follow- 
ing may be mentioned: 


Frotoxide of copper: 0). = .:CuQs, =339°613: 
Suboxide e wh od eee CUS) =a /4213, 
Chloride a eo ee CUCT == 6602. 
Dichloride < any Ome, CAC Chae 9862: 

a Disulphuret a 2 CGE Sess 7032. 


Protoxide of Copper may ite made either by igniting me- 
tallic copper in contact with air, or by calcining the ni- 
trate. It is a black substance, not decomposable by heat, 
but yielding oxygen with facility to carbon and hydrogen, 
and hence extensively used in organic analysis. It is a 
base, yielding salts of a blue or green color. The sub- 
oxide, called, also, red oxide, occurs native as ruby cop- 
per. It is a feeble base. The disulphuret also occurs 
native, as copper pyrites. 


What is remarkable as respects the alleged atomic weight of uranium ? 
Under what forms does copper naturally occur? What is the process for 
its reduction? What are its properties? Which of its oxides is used in 
organic analysis ? 


296 SALTS OF COPPER. 


Copper is easily detected. Caustic potash gives, with 
its protosalt, a pale-blue hydrate, which turns black on 
boiling. Ammonia, in excess, yields a beautiful purple 
solution ; ferrocyanide of potassium, a chocolate brown 
precipitate ; sulphureted hydrogen, a black; and metallic 
iron, as the blade of a knife, precipitates metallic copper. 


SALTS OF THE PROTOXIDE OF COPPER. 

Carbonate of Copper—The neutral carbonate of cop- 
per is not known; but there are several varieties of di- 
carbonates. One, ich passes under the name of Muiner- 
al Green, 1s formed by precipitating with an alkahne car- 
bonate. It occurs naturally in the form of Malachite. 
Blue copper ore is another dicarbonate; the paint called 
Green Verditer has a similar composition. 

Sulphate of Copper—Blue Vitriol—is prepared for com- 
merce by the oxydation of the sulphuret of copper. It 
crystallizes 1 in rhomboids of blue color, with four atoms of 
water. It is soluble in four times its weight of cold, and 
twice its weight of hot water. It is an escharotic, an as- 
tringent, and has an acid reaction. With ammonia it forms 
a compound of a splendid blue color, which may be ob- 
tained in crystals; with potash, Are it forms a double 
salt. There are also subsulphates of copper. 

Nitrate of Copper, formed by the action of nitric acid on 
metallic copper. It crystallizes in prisms, or in plates. 
It acts with very great energy on metallic tin. ‘There is 
a subnitrate of copper. 

Arsenite of Copper—Scheele’s Green—produced by add- 
ing solution of arsenious acid to the solution of ammonia 
sulphate of copper. . 

Copper yields several valuable alloys. Brass is an al- 
loy of copper and zinc; gun metal, bell metal, and spec- 
ulum metal, of copper and tin. The gold and silver of 
currency contain portions of this metal; it communicates 
to them the requisite degree of hardness. 


How may copper be detected? Under what ferms do the carbonates 
of copper occur? What are the method of preparation and properties 
of the sulphate? Whatis Scheele’s green? What are brass, gun metal, 
and bell metal? Why is silver and gold coinage alloyed ? 


LEAD. 297 


LECTURE LXV. 


Leapv.—Reduction of Galena—Relations of Lead to Wa- 
ter.— The Oxides of Lead.— Detection of Lead.—Bis- 
MUTH.— SILVER. —Amalgamation.— Crystallization.— 
Cupellation.— Properties of Silver.—Salts of Silver. 


LEAD. Pb==1063°6: 

LeEApD occurs under various mineral forms, but the most 
valuable one is galena,a sulphuret. From this it is read- 
ily obtained. The galena, by roasting in a reverberatory 
furnace, becomes partly converted into sulphate of lead ; 
the contents of the furnace are then mixed, the tempera- 
ture raised, and the sulphate and sulphuret produce sul- 
phurous acid and metallic lead, the action being 


Bb OO fo Oi we es. oe On Be. 


Lead is a soft metal, of a bluish-white color. Its spe- 
cific gravity is 11°381. It melts at 612° F., and on the 
surface of the molten mass an oxide (dross) rapidly forms. 
At common temperatures it soon tarnishes. In the act 
of solidifying it contracts, and hence is not fit for castings. 
It possesses, at common temperatures, the welding prop- 
erty ; two bullets will cohere if fresh-cut surfaces upon 
them are brought in contact. Under the conjoint influ- 
ence of air and water lead is corroded, a white crust of 
carbonate forming. But when there are contained in the 
water small quantities of salts, such as sulphates, these 
form with the lead insoluble bodies, which, coating its 
surface over, protect it from farther destruction. For 
this reason, lead pipe can be used for distributing water 
in cities without danger. Lead is one of the least tena- 
cious of the metals. The tartrate of lead calcined in a 
tube yields one of the best pyrophori. On bringing it 
into the air at common temperatures, it spontaneously 
1gnites. 

Of the compounds of lead, the following are some of 
the more important : 


——4 


Under what form does lead chiefly occur? How is galena reduced? 
Why can not lead be used for castings? What is the action of pure wa- 
ter, and water containing salts, upon it? 


298 COMPOUNDS OF LEAD. 


Protoxide oflead . .. . . PbO =111°613. 
Sesquioxide “ . . . . . PbgO3 = 231°239. 
Peroxide ENG oe ge 1 Treen 
Redoxide “ .. . . ~ £b30,4 = 342°852. 
Chloride Ss ee te pe ee eee Laes 
Iodide Cp PY SPD ea 2992. 
Sulphuret fet Pos ahs 


The protoxide is made by heating lead in the air; it is 
a yellow body, which fuses at a bright red heat. In the 
first state it is called massicot; in the latter, litharge. It 
yields a class of salts, being a base. It is slightly soluble 
in water. The peroxide is made from red lead by di- 
gesting it with nitric acid, which dissolves out the protox- 
ide, and leaves the substance as a puce colored powder. 
The red oxide, or red lead, is made by calcining lead in 
a current of air at 600° or 700° F. It is used in the 
manufacture of flint glass. The chloride is made by the 
action of hot hydrochloric acid on protoxide of lead: on 
cooling, it is deposited in crystals. The iodide is formed 
when any soluble iodide is added to a protosalt of lead ; 
it is a beautiful yellow precipitate, soluble in boiling 
water, forming a colorless solution, which, on cooling, de- 
posits golden crystals. The sulphuret is galena; it crys- 
tallizes in cubes, and has a high metallic lustre. 

Lead is easily detected by sulphureted hydrogen, which 
throws it from its solutions as a deep brown or black pre- 
cipitate, and by the iodide of potassium or chromate of 
potash, which gives with it a yellow precipitate. Sul- 
phuric acid yields with its salts a white insoluble sulphate 


of lead. 


SALTS OF THE PROTOXIDE OF LEAD. 

Carbonate of Lead— White Lead—Ceruse.—This salt 
forms as a white precipitate when an alkaline carbonate 
is added to a solution of a salt of lead. Large quantities 
of it are consumed in the arts as white paint. Jor com- 
merce it is procured by mixing litharge with water con- 
taining a small proportion of acetate of lead; carbonic 
acid gas is then sent over it, and the carbonate rapidly 
forms. It is also made by exposing metallic lead in 
plates to the action of the vapor of vinegar, air, and moist- 
ure, the metal becoming oxydized and carbonated. 


What is massicot? How is it prepared 1 What is litharge? How 
is the peroxide prepared? How is minium made? How may lead be 
detected? Mention some of the methods by which white lead may be 
made. 


BISMUTH.—SILVER. 299 


Nitrate of Lead may be formed by dissolving litharge 
in dilute nitric acid ; it crystallizes in opaque white octa- 
hedrons, which dissolve in seven or eight times their 
weight of cold water. They contain no water of crystal- 
lization, and are decomposed at a red heat, as stated in 
the description of nitrous acid. By the action of ammo- 
nia, three other nitrates of lead may be obtained. 

Among the alloys of lead are the soft solders. Two 
parts of lead and one of tin constitute plumber’s solder ; 
one of lead and two of tin, fine solder. 


BISMUTH: Bus=. 7107; 

Bismutu is found both native and as a sulphuret. It is 
of a reddish color, melts at 497°, and may be obtained in 
beautiful cubic crystals by cooling a quantity of it until 
solidification commences, then breaking the surface crust 
and pouring out the fluid portion. 

When bismuth is dissolved in nitric acid, and the solu- 
tion poured into water, the white subnitrate is deposited, 
once used as a cosmetic; when this is washed, and sub- 
sequently heated, the protoxide is left. There is also a 

eroxide. 

Fusible metal is an alloy of eight parts of bismuth, five 
of lead, and three of tin; it melts below the boiling point 
of water, and may be obtained in crystals. 

SILVER. Ag = 108-31. 

Sitver is found native, and as a sulphuret and a chlo- 
ride, occurring, also, with a variety of other metals, and 
in small proportion with galena. When disseminated as 
a metal through ores, it may be collected from them b 
amaleamation with quicksilver, and, on distilling, the 
quicksilver is driven off. 

When it is obtained from the sulphuret, that ore is 
roasted with common salt, which changes it into a chlo- 
ride. This, with the impurities with which it may be 
associated, is put into barrels, which revolve on an axis, 
along with water, pieces of iron, and metallic mercury ; 
the iron reduces the chloride to the metallic state, and 
the silver amalgamates with the mercury. This is washed 
from the impurities, strained through a bag to separate 


What change does the nitrate undergo ataredheat? Of what are the 
common solders composed? What are the properties of bismuth? What 
is fusible metal? Under what forms does silver commonly occur? How 
is it reduced from the sulphuret ? 


300 CRYSTALLIZATION.—~CUPELLATION. 


the excess of mercury, and the residue is driven off by 
distillation. 

The extraction of silver, when it occurs in small quan- 
tity with lead, has been recently much improved by the 
introduction of the process of crystallization. It depends 
upon the fact that an alloy of lead and silver is more fusi 
ble than lead. A large quantity of argentiferous lead is 
melted and allowed to cool. As the setting goes on, the 
first portions which solidify are pure lead; they may be 
removed by iron colanders, and by continuing the process 
there is finally left a portion containing all the silver. 
This is exposed to a red heat, and a stream of air direct- 
ed over it; oxydation of the lead takes place, and the 
htharge is removed by the blast, the process being finally 
completed by cupellation. 

A cupel is a shallow dish made of bone ashes, and is 
very porous. In this, if an alloy of lead and silver be heat- 
ed with access of air, the lead oxydizes, and, melting into 
a glass, soaks into the cupel, or may be driven from the 
surface by a blast of air directed from a bellows. At the 
Same time, any copper or other base metal oxydizes and 
is removed along with the lead. ‘The completion of the 
process.is indicated by the silver assuming a certain brill- 
1ancy, or flashing, as the workmen term it. 

Silver is a white metal capable of receiving a brilliant 
polish. It is malleable and ductile, an excellent conduct- 
or of heat and electricity. Its specific gravity is 10-5. It 
melts at 1873° F., and when melted absorbs a large quan- 
tity of oxygen, giving it out again as soon as it SOLnoe 
and assuming a frosted or porous appearance. The pres- 
ence of a minute quantity of copper prevents this effect. 
Silver is so soft that, tor making plate or coins, it requires 
to be alloyed with a portion of copper; from this it may 
be purified by dissolving it in nitric acid, and precipitating 
the silver as chleride by a solution of common salt. Sil- 
ver shows little disposition to unite with oxygen, though 
it tarnishes readily by the action of sulphureted hydrogen. 
It yields three oxides, but of its compounds the following 
are the most important : 

What is the process of amalgamation? What is the process of erystal- 
lization? What is the process s of cupellation? What are the properties 


of silver? Why does it frequently require to be alloyed with copper? 
What remarkable relation does it possess to oxygen? 


“. 


COMPOUNDS OF SILVER. 301 


Protoxide of silver . . . . AgO ==116°323. 
Chloride i 2... « AGCL=143'78. 
Iodide Si oe \e AGL = 29448. 
Sulphuret be : AgS =124-43. 


The protoxide may be made by the action of caustic 
potash on a solution of nitrate of silver, or by boiling re- 
cently-prepared chloride in potash. Itis a dark powder, 
which may be reduced by heat alone. The chloride is 
sometimes found native, as horn-silver, and may be made 
by precipitation from the nitrate by hydrochloric acid, 
or a soluble chloride. Like the iodide, it turns dark on 
exposure to the indigo rays, and hence is used in photo- 
genic drawing. The sulphuret is produced whenever sul- 
phureted hydrogen acts on oxide of silver, or even metal- 
lic silver; it is a black compound. 

Silver is easily detected by precipitation as a chloride : 
a curdy, white precipitate, insoluble in water, but soluble 
in ammonia. It turns dark on exposure to the sun. 


SALTS OF THE PROTOXIDE OF SILVER. 

Nitrate of Silver—Lunar Caustic—procured by dissolv- 
ing silver in nitric acid, diluted with twice its weight of wa- 
ter. It crystallizes in tables which are not deliquescent and 
contain no water of crystallization. It enters into fusion 
at 426° F’., but at higher temperatures undergoes decom- 
position. It is frequently cast into small sticks and used by 
surgeons as a cautery. It is soluble in its own weight of 
cold and half its weight of hot water, and, when in contact 
with organic matter, turns black in the rays of the sun. 

Ammoniuret of Silver—Berthollet’s Fulminating Silver — 
is formed by digesting precipitated oxide of silver in am- 
monia. It explodes with the utmost violence under the 
feeblest friction, with the evolution of nitrogen and the 
vapor of water. 


How may the protoxide be prepared?) What changes do the chloride 
and iodide exhibit under the influence of light? How may silver be de- 
tected? -How is lunar caustic made ? 


Cc 


302 MERCURY. 


LECTURE LXVI. 


Mercury.—Process of Reduction — The Liquid State of. 
—Its Oxides —Calomel and Corrosive Sublimate.-—De- 
tection of Mercury —LIts Salts —Amalgams.—Goup.— 
Chloride of —Purple of Cassius—PaLLapiIumM.—PLa- 
TInuM.—Its Catalytic Effects —Platinum Black —Irww- 
1uM.—Ruopium. | 

MERCURY. Hg = 202. 

Mercury may be obtained from the bisulphuret (cin 
nabar) by distillation with iron filings. It is also, to a 
certain extent, found native. 

The striking characteristic of mercury 1s its liquid condi- 
tion. Its melting point is the lowest of that of any of the 
metals, being —39° I’. Its specific gravity at 47° F. is 
13°545. It boils at 620° IF. Kept at that temperature in 
the air for a length of time, it produces red oxide; but 
at common temperatures it is not acted on by the air. It 
may be freed from impurities for the purposes of the lab- 
oratory, by being kept in contact with dilute nitric acid. 
It gives the following compounds of interest : 


Protoxide of mercury . .. . HgO = 210:013. 
Peroxide : se 6 oe ee Os == OumOoG, 
Protochloride “ ob ge teh Th eae es ee, 
Bichloride id ar ps we Ae Oty = Rie ea 
Protosulphuret “ « sts. Lee aol, 
Bisulphuret WY : . HeS, me ET 


Thé protoxide may be made by triturating calomel 
with potash water in a mortar. It is a black powder, 
which is decomposed by light or any of the reducing agents. 
The peroxide may be formed, as stated above, by the ac- 
tion of air on hot mercury, but more easily by disselving 
mercury in nitric acid and evaporating and heating the 
salt until no more fumes of nitrous acid are evolved. Itis 
a red powder, and when warmed becomes almost black, 
the color returning as the temperature descends. Like 
the former, it is a base, and yields a class of salts. 

The Protochloride, or Calomel, may be made by adding 
hydrochloric acid to the protonitrate of mercury, or by sub- 

Under what forms does mercury commonly occur? What is the most 


striking property of this metal? How may it be purified? What are 
the properties of the protoxide and peroxide? What is calomel? 


4 
\ 


—" 
ae? “Ss 


COMPOUNDS OF MERCURY. 303 


liming a mixture of bichloride of mercury and mercury. 
It is a white powder, insoluble in water, and darkens 
slowly by exposure to sunshine. The dzchloride (or Cor- 
rosive Sublimate) is formed when mercury burns in chlo- 
rine gas, but more economically by sublimation from a 
mixture of persulphate of mercury and common salt. It 
is a heavy, white, crystalline body, soluble in water, has 
a metallic taste, and is poisonous. The antidote for it is 
albumen (the white of an egg). 

Of the sulphurets of mercury, the protosulphuret is 
black, and the bisulphuret commonly red; in this case it 
passes in commerce under the name of vermilion, and is 
used asa paint. It can be obtained, however, quite black, 
a peculiarity already observed in the case of' the perox- 
ide, and still more strikingly in the biniodide, which may 
be sublimed in beautiful yellow crystals, which become 
of a splendid scarlet color by merely being touched. 

Mercury may be detected by being precipitated from 
its soluble combinations by metallic copper as a metal. 
Its Salts, either alone or with carbonate of soda, heated in 
a tube, yield metallic mercury, which volatilizes. 


SALTS OF THE OXIDES OF MERCURY. 

Nitrates of the Oxides of Mercury.—When cold dilute 
nitric acid acts on mercury it gives rise to neutral or basic 
protosalts, as the acid or mercury is in excess; if the acid 
be hot, a pernitrate forms; these salts are decomposed by 
an excess of water, giving rise to basic compounds. The 
neutral pernitrate exists in solution only. 

Persulphate of Mercury is formed by boiling sulphuric 
acid and mercury, and evaporating to dryness. It occurs 
in the form of a white granular mass, and is decomposed 
by water, giving a yellow precipitate, a subsulphate call- 
ed Turpeth Mineral. 

The alloys of mercury are called amalgams ; the amal- 
gam of tin is used for silvering looking-glasses, and that 
of zinc for exciting electrical machines. 


GOLD. | Au = 199°2. 
Gold is found native, and may be obtained by washing 


What is corrosive sublimate? What.is the antidote to it? For what 
purpose is the bisulphuret employed? What change occurs to the yel- 
low biniodide when itis touched? How may mercury be detected? . How 
are the protonitrate and the persulphate prepared? Under what forms 
does gold occur ? 


304 GOLD. 


or by amalgamation with mercury. It may be purified 
from silver by quartation; that is, fusing it with three 
times its weight of silver, and then acting on the mass 
with nitric acid. The gold is left as a dark powder. 
From all other metals gold is distinguished by its yel- 
low color. Its specific gravity is 19-3. It melts at 20169 
IF’, -It is the most malleable of all the metals, as is proved 


thousands of years. No acid alone dissolves it; but it is 
soluble in aqua regia, and also by chlorine. 

It can, however, be made to yield two oxides, a pro- 
toxide and a teroxide ; and two chlorides having the same 
constitution; the terchloride is formed by the action of 
nitromuriatic acid (aqua regia) on gold. When evapora- 
ted, it yields red, deliquescent crystals. Deoxydizing 
agents, such as protosulphate of iron, reduce it to the me- 
tallic state; this is probably due to their decomposing 
water and presenting hydrogen to the chloride. Hydro- 
gen gas decomposes the terchloride, and, by heating it, it 
first changes into the protochloride and then into metallic 
gold. With a solution of tin it forms the Purple of Cas- 
sius. ‘This and the action of protosulphate of iron serve 
as a test for it. 


PALLADIUM. Pd=53°3. 

Palladium is found associated with platinum, and is 
best obtained from the cyanide of palladium by ignition. 
It is a white metal, requiring a high temperature for fu- 
sion; specific gravity 11°5. It does not tarnish in the air, 
is dissolved by nitric acid and aqua regia, is one of the 
welding metals, and, when heated, acquires a purple oxy- 
dation like watch spring. It is used to some extent by 
dentists. Its compounds are not of importance. 


PLATINUM. Pt = 98°84. 
Platinum is found native, but always associated with 
other metals. It is obtained by first forming a chloride 
of platinum and ammonium; this, when ignited, leaves 


What is quartation? What are the properties of this metal? How 
many oxides does it yield? How is the terchloride prepared? What is 
the purple of Cassius? With what metal is palladium generally associ- 
ated? What are its properties? What superficial effect takes place 
when it is heated in the air? How is platinum obtained from its ores ? 


PLATINUM. 305 


pure spongy platinum, which being exposed to powerful 
pressure, and then alternately made white hot and ham- 
mered, becomes a solid mass. 

Platinum is a white metal. Its specific gravity is very 
high, being 21°5. It can not be melted in a furnace, but 
fuses before the oxyhydrogen blow-pipe. It is a welding 
metal,.and on this fact its preparation depends. It is very 
malleable and ductile, is not acted upon by oxygen, air, 
or any acid alone, but dissolves in aqua regia. It pos- 
sesses the extraordinary property of causing hydrogen 
and oxygen to unite at common temperatures, an eflect 
which takes place with remarkable energy when the 
metal is in a spongy state. A jet of hydrogen falling 
upon spongy platina in the air makes it red hot, and pres- 
ently after the gas takes fire. It also brings about the 
rapid transformation of alcohol into acetic acid, and ya- 
rious other chemical changes. 

If a quantity of ether be poured into Fig. 268. 

a glass jar, Ig. 268, and a coil of pla- 
tinum wire, recently ignited, be intro- 
duced, the metal continues to glow so 
long as any ether is present. 

Platinum is invaluable to the chem- 
ist. It furnishes a variety of imple- 
ments of great value, and is met with 
under the forms of crucibles, tubes, i 
wire, foil, &c. all! 


Platinum Black is prepared by slow- = — ———— 
ly heating to 212° a solution of chloe = “0 
ride of platinum, to which an excess of carbonate of soda 
and some sugar have been added. It is a dark powder, 
and possesses the property of determining a variety of 
chemical changes with much more energy than platinum 
in mass. 

Platinum can be caused to yield two oxides, which are 
not of any importance; and two analogous chlorides, of 
which the bichloride, which is the common platinum salt, 
is made by dissolving the metal in nitromuriatic acid, 


What is the specific gravity of this metal? By what acid may it be 
dissolved? What remarkable relations does it possess to hydrogen gas ? 
Under its influence, what is alcohol transmuted into? What is platinum 


black ? 
Cc.2 


306 IRIDIUM.—RHODIUM. 


and evaporating to a sirup. It is soluble in water and 
alcohol, and is used for detecting the salts of potash. 


IRIDIUM. Jr=98°'84. 

Iridium is associated with platinum. It is said to have 
been found of specific gravity 26°00. Dr. Hare has ob- 
tained it 21°8; it is, therefore, the heaviest of the metals. 
Its name is derived from the different colors (iris) of its 
compounds. 

RHODIUM. R=52°2. 
Like the former metal, rhodium is associated with the 
latina ores. It is a hard white metal; its specific grav- 
ity is 11:00, and is sometimes used to form tips to metal- 
lic pens. 


What are the properties of iridium? What are those of rhodium? 


PART IV. 


ORGANIC CHEMISTRY. 


LECTURE LXVII. 


Peculiarities of Organic Bodies—Their Constituent Ele- 
ments.—Prone to Decomposition.—Carbon always Pres- 
ent.—Compound Radicals —Doctrine of Substitution — 
T'ypes.—Action of EHeat.—Eremacausis.— Propagation 
of Decay.— Action of Acids and Alkalies. 


Tue theory of molecular arrangement, which has been 
already given, forms the foundation of organic chemistry. 
It asserts that the characters of compound bodies do not 
alone depend on the nature of their constituent elements, 
nor even on the relative amount of those elements; but 
that variation of physical forms may result from atoms of 
the same name and of the same number arranging them- 
selves in subordinate groups, which groups then unite 
with each other. 

The leading ultimate elements of organized bodies are 
carbon, hydrogen, nitrogen, and oxygen. Almost all or- 
ganic hodies arise from variations in the number and 
grouping of identical elements. 

Now a partial consideration of the conditions under 
which the theory of molecular arrangement acts, exhibits 
to us a most striking difference in the nature of the com- 
pounds formed upon its principles and the compounds 
heretofore described as examples of inorganic chemistry. 
In the one, peculiarity of grouping is the grand feature ; 
in the other, the character of the combining elements. 
Urea differs from the cyanate of ammonia in the arrange- 
ment of its constituents only; but the leading mark of dis- 
tinction between sulphuric and phosphoric acids is, that 
the one contains sulphur and the other phosphorus. 

The number of substances which, besides the four men- 


On what do the characters of compound bodies depend? Of what four 
leading elementary bodies are organic substances chiefly composed? In 
what striking respect do these substances differ from imorganic ones ? 


308 CHARACTERS OF ORGANIC BODIES. 


tioned above, enter into the composition of organic bodies 
is very limited. Among such may be mentioned potash, 
soda, lime, magnesia, oxide of iron, chlorine, fluorine, sul- 
phur, phosphorus, and silica. Some of those bodies, such 
as alumina, which appear to take the lead in inorganic 
productions, are here scarcely seen. 

While the laws of inorganic chemistry appear to be 
fully in operation as respects the bodies on the study of 
which we are now entering, there are some peculiarities 
which deserve to be pointed out. The remarkable insta- 
bility, or proneness to decomposition, which so many of 
them exhibit, generally tends to the production of second- 
ary compounds of a much more stable nature. At ared heat 
all organized bodies are decomposed ; and as the ele- 
ments ee which they consist are Sndowan with the most 
energetic affinities, any extensive elevation of tempera- 
ture tends to impress upon them a change. With but few 
exceptions, the attempts which have hitherto been made 
to produce them artificially have been abortive ; but this is, 
probably, rather due to our want of knowledge than any 
intrinsic impossibility 1 in effecting such combinations 

With the exception of a few bodies such as ammonia, 
which, in point of fact, belong rather to inorganic chem- 
istry, all organized bodies contain carbon. Of late, by in- 
direct processes, chemists have succeeded in obtaining 
pseudo-organized compounds, into the constitution of 
which such bodies as platinum and arsenic enter. 

In inorganic chemistry we see a constant disposition to 
the binary form of union: a disposition which is well rep- 
resented by the electro-chemical theory. Thus, potassi- 
um unites with oxygen, two bodies together, to aan pot- 
ash; and this, again, with sulphuric acid, two bodies to- 
gether, to form sulphate of potash. In very many instan- 
ces, the same thing can be traced in organic chemistry ; 
only here, instead of having such bodies as chlorine or 
iodine, potassium or sodium to deal with, we find com- 
pound bodies which discharge analogous functions. These 
bodies go under the name of compound radicals. The 
may be divided into distinct groups, some discharging the 


W hat other elements are found among inorganic bodies? In their de- 
composition, what do they generally produce ? Can any of them with- 
stand a red heat? Can they be formed by artificial means? What is 
meant by compound radicals? 


COMPOUND RADICALS. 309 


duty of electro-negative, some of electro-positive, and 
some of indifferent bodies. In several cases they have 
been insulated, but in others they remain as yet as ideal 


or hypothetical bodies. 
Tabie of Compound Radicals. 


Amidogen. Iridiocyanogen. Acetyle. 
Oxalyle. Sulphocyanogen. Kakodyle. 
Cyanogen. Mellone. Methyle. 
Ferrocyanogen. Uryle. Formyle. 
Ferridcyanogen. Benzyle. Cetyle. 
Cobaltocyanogen. Salicyle. Amyle. 
Chromocyanogen. Cinnamyle. Glyceryle. 
Platinocyanogen. Ethyle. 


The qualities of bodies depending as much on the mode 
of arrangement of their constituent particles as on the 
chemical nature of those particles, it has been found con- 
venient to arrange them in groups, according to their 
type of structure; thus, for instance, in the former de- 
partment of chemistry, such bodies as hydrochloric, hy- 
driodic, hydrobromic acids may be arranged together as 
belonging to one type; and from the first of these all the 
rest may be conceived as arising, by substituting an atom 
of iodine, bromine, fluorine, &c., for the atom of chlorine 
which it contains. 

The bodies which can thus be substituted for each 
other appear to have certain relationships; for the sub- 
stitution of a given substance can not take place indiscrim- 
inately by all other bodies. As a general rule, in inor- 
ganic combinations, electro-negative bodies can only be 
substituted by electro-negative, and electro-positive by 
electro-positive. But many of the most prominent cases 
in organic chemistry are precisely the reverse. In them, 
for example, we find chlorine, a powerful electro-nega- 
tive, taking the place of hydrogen, an equally powerful 
electro-positive body, and, in the compound, discharging 
all its functions. For these reasons, it has been supposed 
that the electro-chemical theory fails to furnish any ex- 
planation; but I have proved that chlorine, like many 
other bodies, can assume different allotropic states ; at one 
time being an active electro-negative body, and at an- 
other quite passive. Moreover, it ought not to be for- 


What compound radicals are known? Under what circumstances can 
bodies be substituted for each other? Is there any difference in this re- 
spect between inorganic and organic bodies ? 


310 DESTRUCTION OF ORGANIC COMPOUNDS. 


gotten that hydrogen, in relation to carbon, is as much an 
electro-negative body as chlorine itself. 

A. chemical type is, therefore, a system, or group of 
atoms of a certain nation arranged in a certain relation- 
ship with each other. From this each atom may be dis- 
placed, and one of another kind substituted im its stead; 
and this may be carried forward until not one of the orig- 
inal atoms is left, the new group officiating in all respects 
like its predecessor. But should one of the atoms be 
displaced, and no new one substituted for it, then, the re- 
maining atoms changing their position, the type is broken 
up and a new one is the result. 

Organic compounds, being for the most part composed 
of carbon, hydrogen, nitrogen, and oxygen, exhibit a con- 
stant tendency to break up into subordinate groups, and 
eventually to give rise to the production of the simpler 
binary bodies, carbonic acid, water, and ammonia. The 
carbon constantly inclines to unite with oxygen to form 
carbonic acid, the hydrogen, in the same manner, to form 
water, or, with the nitrogen, to produce ammonia; and 
these tendencies may be satisfied in a variety of ways. 
Elevations of temperature in the open air at once give 
rise to carbonic acid, water, and free nitrogen; or if in 
close vessels out of the contact of air, to an extensive se- 
ries of compounds, differing in each case with the sub- 
stance exposed, and of a less complex constitution. Even 
in the air, at common temperatures, a slow action often 
goes on, as in the decay of wood or the souring of wine ; 
hence called eremacausis (slow combustion). 

When a combustible substance is ignited in the air at 
one point, the burning presently spreads throughout the 
whole mass; and in ‘the slow combustion, eremacausis, 
the same takes place. A substance undergoing such a 
change, if placed i in contact with another capable of un- 
dergoing it, propagates its effect throughout the whole 
mass. For this reason, the decay of yeast, a ferment, im- 
presses a metamorphosis on sugar, compelling it to give 
off carbonic acid gas ; and putrefaction of fresh meat is eas- 
ily brought on by the contact of putrid animal matter. 


What is a chemical type? Under what circumstances do new types 
result? What are the binary bodies eventually produced? What is the 
result of elevation of temperature inthe openair? What inclose vessels ? 
What is meant by eremacausis? In what respect does eremacausis re- 
semble common combustion ? 


THE NON-NITROGENIZED BODIES. 311 


Nitric, sulphuric, and other strong acids impress striking 
changes when heated with organic matters ; thus, when 
the former acts on starch, oxalic acid is formed; when 
sulphuric acid acts on oxalic, it totally destroys it, resolv- 
ing it into carbonic acid, carbonic oxide, and water. In 
the same manner, also, basic bodies produce striking chang- 
es, generally giving rise to the production of acids, and the 
evolution of hydrogen and ammonia. 

In the present state of organic chemistry, it is im pos- 
sible to present a perfect system of arrangement, as in in- 
organic chemistry, or one approaching to the finish of that 
department. The course, therefore, which I shall now 
take is recommended rather for its usefulness in facilita- 


ting study than for the propriety of its classification. 


LECTURE LXVIII. 


Tue Non-nirrocenizep Bopirrs.— The Starch Group.— 
Starch.—Action of Iodine— Various Forms of Starch. 
—Production of Dextrine.—Action of Diastase.—Leio- 
come.— Cane Sugar.—Glucose.— Distinction between 
Cane and Grape Sugar.—Milk Sugar.—Gum.—Lig . 


nine. 


THE non-nitrogenized bodies, which we shall first con- 
sider, are characterized by the peculiarity that they form 
a group, each member containing twelve atoms of carbon, 
united with hydrogen and oxygen in the proportions to 
form water. They are for the most part indifferent bod- 
les. 

The Starch Group. 


Starchy poco os RA OPT s PN Fe 

Cane sugar (crystallized) me, ee Ceti ys 

Grapesagar) Cees ii trie ACnenOn 

Milk BUDE a hehe spy os aay re pe eel « Cig H2O iz. 

ETI ee aa ree Gemdien® eee sy pita 

Hiening 2 SP) OS ees Gistie Oe 
&e. &e. 


Starch—Fecula ( C\,H,)0,.)—is found abundantly in the 
vegetable kingdom, and may be obtained from potatoes 


What is the effect of strong acids and alkalies on organic bodies? How 
many carbon atoms does each member of the amyle group contain? In 
what proportion are their oxygen and hydrogen? Mention some of the 
chief bodies of this group. From what sources, and in what manner, is 
starch obtained ? 


312 VARIETIES OF STARCH. 


by rasping and washing the mass upon a sieve, the starch 
being carried off by the water. It may also be obtained 
from flour by making it into a paste with water and then 
washing it. The starch separates, and gluten is left be- 
hind. 

It is a white substance, commonly met with in irregu- 
lar prismatic masses, which shape it assumes while drying. 
It is insoluble in cold water, and also in alcohol, and con- 
sists of granules of different sizes, as it is derived from 
different plants, those of the potato being about the two 
hundred and fiftieth of an inch in diameter. 

When starch is heated in water, the covering mem- 
brane of each granule bursts open, and the interior matter 
dissolves out. If the proportion of starch be considerable, 
the whole forms a jelly-like mass, which may be dried in 
a yellowish body, having the same constitution as starch 
itself. Gelatinous starch passes under the name of Amz- 
dine. 

With free iodine, starch strikes a deep blue color. 
When water containing this compound is heated to 212° 
F’., the color totally disappears, and is not restored on cool- 
ing; but if the source of heat be removed as soon as the 
color disappears, and before the temperature reaches 212° 
F., the color returns. Starch and iodine constitute an ex- 
ceedingly delicate test for each other. 

In commerce, starch is found under various modifica- 
tions, such as Arrow-root, Tapioca, Cassava, Sago. It 
forms an important article of respiratory food. Inuline, 
which is derived from the dahlia and other plants, is a sub- 
stance approaching starch in many respects. 

When starch is boiled in water with a small quantity of 
sulphuric acid, it changes into Dextrine,asubstance of the 
same composition; the acid being subsequently removed 
by carbonate of lime and filtration, that body is procured 
on evaporation ag a gummy mass. But if the ebullition 
be continued for a longer time, the dextrine disappears 
and grape sugar comes in its stead. Starch may also be 
converted into grape sugar by the action of a peculiar 
ferment, Diastase, which is contained in an infusion of 


What is the size of its granules? What is the effect of hot water on 
it? Whatis amidine? What is the action of iodine on starch? Mention 
some other varieties of starch. How is it converted into dextrine? How 
into grape sugar? What is diastase? 


CANE SUGAR. 313 


malt. Gelatinous starch may, in the course of a few min- 
utes, at 160° I’., be converted into dextrine by this sub-. 
stance, and soon after into sugar. In either of these cases 
the presence of atmospheric air is not required ; the final 
action being that the starch simply assumes three atoms of 
water, and becomes converted into grape sugar. 

When baked at a temperature of about 400° F., starch ° 
becomes soluble in water, and passes in commerce under 
the name of British Gum, or Lewocome. 

Cane Sugar (C,,H,O,+2HO) is found abundantly in 
the juices of many plants, and is chiefly extracted for com- 
mercial purposes from the sugar-cane, which, being crushed 
between rollers, yields a juice, which is mixed with lime 
and boiled; a coagulum having been removed from it, it 
is rapidly evaporated at as low a temperature as possible, 
and then crystallized. In this state, after a brownish sir- 
up, molasses, has drained from it, it passes in commerce un- 
der the name of Muscovado, or brown sugar. ‘This is pu- 
rified by boiling in water with albumen, which, coagulat- 
ing, separates many of the impurities; the solution is then 
decolorized by animal charcoal, evaporated, solidified in 
conical vessels, and, being washed with a little clean sirup, 
is thrown into commerce as loaf-sugar. Sugar is also ob- 
tained from the sap of the maple-tree, and from beet-root. 

From a strong solution sugar crystallizes in rhombic 
prisms, which are colorless; they pass under the name of 
Sugar Candy. It is soluble in one third its weight of cold 
water, and in any quantity of hot. It has a sweet and 
proverbially characteristic taste. When heated, it melts, 
and gives rise to a yellowish, transparent body, called 
Barley Sugar. But if kept at a temperature of 630° F., 
it turns of a reddish-brown color, constituting Caramel. 
Sugar unites with various bodies, such as lime and oxide 
of lead, and with common salt yields a crystallized prod- 
uct. By caseine it is transformed into lactic acid. 

Grape Sugar—Frut Sugar—Glucose—Starch Sugar 
—Diabetic Sugar (C\,H,,0.,)—is the substance just de- 
scribed as arising from the transmutation of starch under 
the influence of acids. It occurs naturally in many vege- 
table juices and in honey. _ 


What is its action on starch? How is British gum formed? From 
what sources, and by what means, is cane sugar derived? What are itg 
properties? By what means is caramel formed? 


Do 


314 GRAPE AND MILK SUGAR. 


Compared with cane sugar, it is much less soluble in 
water, and less disposed to crystallize. It requires 14 
parts of water for solution. It may be distinguished by 
its action with caustic alkalies and sulphuric acid, the form- 
er turning it brown and the latter dissolving it without 
blackening, while cane sugar is little acted on in the form- 
er instance, and blackened i in the latter. The two yari- 
eties may also be distinguished by being mixed with a so- 
lution of sulphate of copper, to which, if caustic potash be 
added, blue liquids are obtained, and these being heated, 
the grape sugar throws down a green precipitate, which 
turns deep red, the solution being left colorless: the cane 
sugar alters very slowly, a red precipitate gradually form- 
ing, and the liquid remaining blue. Grape sugar, like 
cane sugar, gives with common salt a crystallized com- 
pound. When heated to 212° F. it loses two atoms of 
water, and becomes C,,.H,,O,». 

Milk Sugar—Lactine (C\.H,,0,,)—may be obtained 
by evaporating whey to a sirup, and the crystals which 
then form are to be purified by animal charcoal. It is 
sparingly soluble, requiring five or six times its weight of 
water. The cr ystals are gritty between the teeth. It is 
through the alcoholic fermentation of this body that the 
Tartars procure intoxicating milk. 

Besides the foregoing, there are several subordinate 
varieties of sugar, among which may be cited 


Hrpotisucar it. sue ac Uiekak- oe elie Qiss 
Eucalyptus sugar . ... . . Ci2MisaOna; 
and others, as liquorice sugar, mushroom sugar, or man- 


nite, &c, 

Gum.—Gum Arabic is obtained from several species of 
the mimosa or acacia, from the bark of which it exudes; 
is obtained in white or yellowish tears, of a vitreous as- 
pect. It dissolves in cold water, forming mucilage, from 
which it may be precipitated pure, as Arabine, by alcohol. 

Bassorine is the principle of Gum Tragacanth ; it does 
not dissolve in water, but merely forms a jelly-like mass. 
With this substance abouid be classed Pectine, the jelly 
obtained from currants and other fruits. This substance 
furnishes Pectic acid by the action of bases. 

What is the difference between cane and grape sugar? By what test 
may they be distinguished? What are the Properties of milk sugar? 


Mention some other varieties of sugar. From what source is gum de- 
rived? What are arabine, bassorine, and pectine ? 


LIGNINE. 315 


Lignine.— This substance, with Cellulose and other bod- 
ies, forms the woody fibre or ligneous tissue of plants. It 
occurs in a state of purity in the fibres of fine linen and 
cotton, and, as is well known, is of perfect whiteness, in- 
soluble in water and alcohol, and tasteless. Strong and 
cold sulphuric acid converts it into a dextrine, as may be 
shown by adding to that substance pieces of linen, taking 
care that the temperature does not rise so as to blacken 
the mixture, which is to be well stirred, and suffered to 
stand for a time. On dissolving it then in water, and 
neutralizing by the addition of chalk, dextrine is obtained ; 
or if, before neutralizing, the solution is well boiled, grape 
sugar is produced. 


LECTURE LXIX. 


Action oF AGENTS ON THE STAaRcH Grovup.—Action of 
Sulphuric Acid on Sugar.—Glucic Acid produced by 
Lime—Melassic Acid.—Action of Nitric Acid.—Pro- 
duction of Oxalic Acid.— Constitution of Oxalic Acid.— 
Its Salts.-—Oxamide.— Saccharic Acid. — Rhodizonic 
and Croconic Acids.— Mucic Acid.— Xyloidine.— Its 
Properties. 

In the preceding Lecture we have already explained 
the change of starch into sugar, and of lignine into dex- 
trine, under the influence of sulphuric acid; and in the 
vegetable world there can be no doubt that these and 
other similar modifications arise from the action of many 
causes. On inspecting the constitution of the group, it 
will be seen that, in theory, this is to be done by the ad- 
dition or abstraction of water. 

When melted grape sugar is mixed with strong sul- 
phuric acid, and the diluted solution neutralized with car- 
bonate of baryta, the sulphosaccharate of baryta is found 
in the solution. The Sulphosaccharic acid is a sweetish 
liquid, readily decomposing into sugar and sulphuric acid. 

When, in the process of converting cane sugar into 


How may lignine be prepared? When pure, what is its color, and 
what its relation to water? How may it be converted into dextrine and 
grape sugar? In this change, what is the action impressed on the lignine ? 
How is sulphosaccharic acid made ? 


316 OXALIC ACID. 


grape sugar by boiling with sulphuric acid, the action is 
long continued, a dark-colored substance is formed, con- 
sisting of two differ ent bodies, Ulmine and Ulmic Mek or, 
as they are termed by Liebig, Sacchulmine and Sacchulmic 
Acid. The latter is converted into the former by contin- 
ued boiling in water. . 

When a solution of grape sugar containing lime is kept 
for some time, the alkaline reaction of the lime finally 
disappears through the formation of Glucze Acid, the con- 
stitution of which is C,;H;O;. It is soluble, deliquescent, 
of a sour taste, and yielding, for the most part, soluble 
salts. If grape sugar be boiled with potash water until it 
becomes black, a dark substance may be precipitated by 
an acid. This is Melasinic Acid, its constitution being 
C,,—0;. 

These are some of the less important results of the 
action of acid and alkaline bodies on the starch group ; 
there are others of far more interest. 

Oxaxic Acip (C,0;, HO+2Aq).—Oxalic acid is formed 
by the action of nitric acid on starch or sugar, or any other 
of the starch group, except gum and sugar of milk. One 
part of sugar is to be mixed with five of mitric acid, di- 
luted with | twice its weight of water, and the acid finally 
distilled off until the residue will deposit crystals on cool- 
ing. These, being collected, are to be purified by redis- 
solving and crystallizing. They are oblique rhombic 
prisms, more soluble in hot than cold water, of an in- 
tensely acid taste, and poisonous to the animal economy, 
chalk or magnesia being the antidote. Ovxalic acid also 
occurs naturally in several plants, in union with potash 
or lime. 

As the foregoing formula shows, the crystals of oxalic 
acid contain one equivalent of saline water and two of 
water of crystallization. The latter may be removed by 
exposure to a low heat, the crystals then becoming a 
white powder, and subliming without difficulty. Any at- 
tempt to remove the saline water and isolate the oxalic 
acid (as C,O;) leads to its decomposition. Thus, when 
the acid is heated with oil of vitriol, total decomposition 


What are sacchulmine and sacchulmic acid? What is the constitution 
of glucic acid? What is the action of potash on grape sugar? Describe 
the preparation of oxalic acid. What is the antidote to it? What is 
the action of oil of vitriol on oxalic acid? 


SALTS OF OXALIC ACID. als 


results ; equal volumes of carbonic oxide and carbonic 
acid are set free: for the constitution of oxalic acid is 
such, that we may regard it as composed of an atom of 
each of those bodies : 
Coe wast Oe OG: 

and upon this is founded one of the methods of preparing 
carbonic oxide gas. ‘The gaseous mixture which results 
from the action ef the oil of vitriol is passed, as in Fg. 
243, through a bottle containing potash water, which ab- 
sorbs the carbonic acid, and the carbonic oxide may be 
collected at the water trough. © 

The production of oxalic acid from sugar by nitric acid 
is due to the replacement of hydrogen by an equivalent 
quantity of oxygen. 


Cen Ojg ee iets s oC Oe OG 
that is, one atom of dry sugar with eighteen of oxygen 
yields six atoms of oxalic acid and nine of water. 


Salts of Oxalie Acid. 


There are three potash salts: 1st. Neutral Oxalate of 
Potash, made by neutralizing oxalic acid with carbonate 
of potash ; crystallizes in rhombic prisms, soluble in three 
times its weight of water. 2d. Binowalate of Potash, made 
by dividing a solution of oxalic acid into two parts ; neu- 
tralize one with carbonate of potash, and then add the 
other. It crystallizes in rhombic prisms, has a sour taste, 
and dissolves in forty parts of water. It occurs naturally in 
several plants, as the Oxalis Acetosella. 3d. Quadroxalate 
of Potash. Divide asolution of oxalic acid into four parts ; 
neutralize one and add the rest. It crystallizes in octa- 
hedrons ; less soluble than either of the foregomg. These 
salts are sometimes used for the removal of ink stains 
from linen. 

Oxalate of Ammonia, prepared by neutralizing a hot 
solution of oxalic acid with carbonate ofammonia. It crys- 
tallizes in rhombic prisms, which are efflorescent. Its so- 
lution is used, as has been already stated, as a test and 
precipitant of lime. When exposed to heat in a retort, it 
is, for the most part, decomposed into water, ammonia, 


How is this acid produced from sugar? How many oxalates of potash 
are there? How are they prepared? For what purpose are these salts 
sometimes used ? 

Dod2 


318 SACCHARIC—MUCIC ACIDS, 


carbonic acid;.cyanogen, and other compounds; but a sub- 
stance of the name of Oxamide also sublimes, the consti- 
tution of which is 
C,H: NO, se = eel ge}; 

that is, containing the constituents of one atom of amido- 
gen and two of carbonic oxide. This remarkable sub- 
stance, when boiled with potash, yields, through the de- 
composition of water, oxalate of petash and ammoniacal 
gas. 

Oxalate of Lime occurs naturally, forming the skeleton 
of many lichens, and is obtained, as has just been said, by 
precipitating a lime salt. Itis soluble in nitric acid, and, 
ignited in a covered crucible, is converted into carbonate 
of lime. . 

Saccuaric Acip (C,,H,O,, + 5HO)—Ozalhydric Acid 
—may be made by heating one part of sugar with two 
of nitric acid, diluted with five times its weight of water. 
The resulting liquid is to be diluted, neutralized with 
chalk, and filtered. A solution of acetate of lead throws 
down a precipitate of saccharate of lead, from which the 
acid may be set free by sulphureted hydrogen. It may 
be obtained by evaporation in colorless needles, yields a 
soluble salt with lime, and with nitrate of silver; when am- 
monia is added, gives a white precipitate, which, on be- 
ing warmed, is suddenly reduced, the vessel acquiring a 
mitror-like coating of metallic silver. It is a pentabasic 
acid. 

Ruopizonic Acip (C,O, + 3HO).—A stream of car- 
bonic oxide being passed over red-hot potassium, a dark 
substance results, which dissolves in water, producing a 
red solution of the rhodizonate of potash. The acid itself 
has not yet been isolated, but the potash salt contains three 
atoms of base, and the acid is tribasic. When boiled, it 
changes to a yellow color; Croconic Acid is generated, 
which can be insulated as a yellow body, having the con- 
stitution C,O, + HO. 

Muvcice Aci (C,,H;O,,-+ 2HO).— This acid arises 
when gum or sugar of milk is acted upon by dilute nitric 


Under what circumstances does oxamide form? What is its constitu- 
tion? How is saccharic acid made? Under what circumstances can 
glass be silvered with it? How is the rhodizonate of potash formed? 
What is its composition? How is it changed into croconic acid? Under 
what circumstances does mucic acid form ? 


FERMENTATION. 319 


acid, as in the preparation of oxalic acid by other mem- 
bers of the starch group.. It separates as a white insolu- 
ble body. It forms salts with bases, and requires sixty 
times its weight of boiling water for solution. Decom- 
posed by heat, it yields pyromucic acid. 

Xyxiorwine (O,H,O,, NO;) is made by the action of ni- 
tric acid, specific gravity 1:5, on starch, which is convert- 
ed into a gelatinous body. - When acted on by water it 
yields a white insoluble precipitate, the substance in ques- 
tion. Its origin is apparent from a comparison of the form- 
ula of xyloidine with that of starch. Paper, when dipped 
in nitric acid, and then washed in water, turns into this 
substance. It looks like parchment, and is combustible 
like tinder. Xyloidine is insoluble in boiling water, but 
by the continued action of nitric acid changes into oxalic 
acid. 


LECTURE LXx. 


On THE METAMORPHOSIS OF THE STARCH Group By NI- 
TROGENIZED I*ERMENTS.—Action of Leaven.—Bread.— 
Fermentation of Sugar.— Fermentation of Grape Juice.— 
Primary Action on the Ferment.— Activity of Ferments 
due to Nitrogen.— Effects of Temperature —Production of 
Butyric Acid —Ferments of different Properties.—Pro- 
duction of Wine and intoxicating Liquids. 

In the preceding Lecture we have traced the action 
of the more powerful organic agents on the amyles, and 
seen how a variety of bodies of different characters arise, 
some of which, as oxalic acid, are of very considerable 
importance. 

But there is another system of changes which can be 
impressed on this group of bodies, far more curious in its 
nature, and leading to far more important results. 

When flour, made into a paste with water, is brought 
in contact with Leaven, that is to say, a similar dough, un- 
dergoing an incipient putrefactive fermentation, at a tem- 
perature of 60° or 70° F., bubbles of gas are disengaged, 

Decomposed by heat, what does mucic acid yield? How is xyloidine 


prepared, and what are its properties ? What is the action of leaven on 
flour ? 


320 ACTION OF FERMENTS. 


the paste swells up, and, when baked, forms leavened 
bread. This ancient process, which is now in use all over 
the world, depends on the action of the changing leaven 
being propagated to the sugar which the flour contains. 
The : sugar is resolved ifito alcohol and carbonic acid gas, 
the former of which may be obtained by distilling the | 
dough; and the bubbles of the latter, entrapped in the 
yielding mass, gives to the bread the lightness for which 
it is prized. 

But this process may be better traced by observing 
the phenomena of alcoholic fermentation in the case of 
pure sugar. If we take a solution of sugar in water, it 
may be kept for a length of time without undergoing an 
change ; but if nitrogenized matters, such as blood, albu- 
men, leaven, in a state of putrescent decay, are mixed 
with it, then, ata temperature of 70° F., the sugar rapidly | 


. . . . — . 
disappears, carbonic acid is given off, and alcohol is found 


in the solution. The change is obvious. 
C,,8,,0, . «= ...'2(C,H,0,) + 4(CO,); 


that is, one atom of dry grape sugar yields two of alco- 
hol and four of carbonic acid. The final action, there- 
fore, of the ferment is to split the sugar atom into carbon- 
ic acid and alcohol. 

Of all ferments, Yeast, for these purposes, is the most 
powerful; it is a substance which arises during the fer- 
mentation of beer. It is probable that, in the various 
sugars, the first action is to bring them into the condition 
of grape sugar, and then the metamorphosis ensues. 

By an analogous transformation of the sugar contained 
in fruits, the different wines and other intoxicating liquids 
are formed ; thus, if we take the expressed juice of grapes 
which has not been exposed to the contact of air, it may 
be kept for a length of time without change; but if a sin- 
gle bubble of oxygen is admitted to it, fermentation at 
once sets in, the grape sugar disappears, and alcechol 
comes in its stead, carbonic acid gas being disengaged, 
and the nitrogenized substance, yeast, deposited. Ifa so- 
lution of pure sugar be added, it is involved in the change, 
and portion after portion will disappear; but, finally, the 


What is the action of decaying nitrogenized matter on a solution of sugar? 
Into what bodies does the sugar atom split? What is the action of yeast 
on sugar? Describe the action of yeast on grape juice. 


ACTION OF FERMENTS. 321 


yeast itself is exhausted, and then any excess of sugar re- 
mains unacted upon. 

It is obvious that the primary action is an oxydation 
of the ferment, and the moment its particles are set in 
motion the motion is propagated to the adjacent body, 
the particles of which submit in succession ; and there- 
fore the fermentation is not a sudden action, but one re- 
quiring time. Moreover, itis plain that the action is lim- 
ited; a given quantity of yeast will transmute only a defi- 
nite quantity of sugar. 

The ferments, or bodies which possess this singular 
quality, are nitrogenized bodies; and, inasmuch as non- 
nitrogenized bodies never spontaneously ferment while 
oxydizing, it is to the nitrogen that we are to impute the 
qualities in question. 

Temperature has a remarkable control over ferment 
action. ‘The juice of carrots or beets, fermenting at 50° 
Fahr., will yield alcohol, carbonic acid, and yeast; but 
the same juices, fermenting at 120° Fahr., produce lactic 
acid, gum, and mannite. Under these circumstances, 
circ) alcohol is the product of fermentation at low, 
and lactic acid at high temperatures. 

But when milk ferments at 50° Fahr., lactic acid is the 
chief product, while at 80° Fahr. the casein acts like a 
yeast ferment, the milk sugar becoming transformed into 
grape sugar, and then resolving itself into alcohol and 
carbonic acid. In this instance the action is the reverse 
of the former, lactic acid being the product of a low, and 
alcohol of a high temperature. 

A very remarkable decomposition takes place when 
casein ferment acts on sugar at 80° Fahr. in presence of 
carbonate of lime. Under these circumstances, carbonic 
‘acid gas and hydrogen are evolved, and Butyric Acid ap- 
pears. On comparing the constitution of butyric acid 
with alcohol, it will be seen that the latter contains the 
elements of the former, with an excess of hydrogen; so 
that, during this fermentation, the alcohol atom is divided. 

All ferments possess certain properties in common, but 
each has its specific powers; and the products mick are 


What is the primary action in these cases? Is the action of the fer- 
ment definite? To what element in the yeast is the action due? What 
is the effect of temperature on fermentation? Describe the causes of the 
fermentation of vegetable juices and of milk? Under what circumstances 
does butyric acid form ? 


Sue PREPARATION OF WINES. 


evolved differ in different cases. Most commonly the ac- 
tivity of these bodies is excited by an incipient oxyda- 
tion, the result of which would be to bring the ferment 
itself to a simpler constitution. In this respect, therefore, 
the first stage of fermentation is a combustion at common 
temperatures, or an eremacausis of the ferment itself; 
but this action is speedily propagated to the surrounding 
mass, which becomes involved in the change. What- 
ever, therefore, prevents the incipient oxydation of the 
ferment puts a stop to the whole process. By raising 
their temperature to 212°, and then cutting off the access 
of air, substances which would otherwise undergo a very 
rapid change may be kept for any length of time without 
alteration. On this principle, meats, milk, and other viands 
may be preserved. 

We have now pointed out the peculiarities of ferment 
action, showing that two successive stages may be traced 
in the process; the first arising in the oxydation of the 
ferment, by which its molecules are decomposed; and the 
second, which consists in the propagation of this move- 
ment to the surrounding particles, upon which changes 
are impressed, the nature of which differs with the tem- 
perature and the specific action of the ferment itself. 

Wine is made from the expressed juice of grapes, which, 
containing a nitrogenized body, albumen, when exposed 
to the air ‘undergoes spontaneous fermentation the course 
of the action being, iste The oxydation of the vegetable 
albumen; 2d. The propagation of its action to the grape 
sugar. If the sugar is in excess, the wine remains sweet ; 
if the albumen is in excess, the wine is dry. The wine, 
as soon as the first action is over, 1s removed into casks. 
During these changes, the bitartrate of potash, which 
exists naturally in grape juice, and which, though sparing- 
ly soluble in water, is much less so in alcohol, is deposit- 
ed. It goes under the name of Arvgol. Most other fruit 
juices contain free acid, such as malic or citric ; and hence 
good wine can not be made from them, because, if all the 
sugar is removed, they possess a sharp taste ; and if, as is 


What is the change which the ferment itself undergoes? Whatis the 
effect of cutting off the access of air? What are the two stages of fer- 
ment action ? “What i is the process for the making of wine? When is the 
wine sweet, and when dry? What is argol? Why are other fruit juices 
less proper for making wine than grape juice ? 


ALCOHOL. 323 


commonly the case, a portion is left to correct the acid- 
ity, it is liable to run into a second fermentation. 

Inferior liquids, such as cider, perry, &c., are made 
from other vegetable juices, as those of apples, pears, &c. 
Beer, porter, and ale are made from an infusion of malt, 
which is barley, a portion of the starch of which is trans- 
posed into sugar by partial germination. The principles 
of the fermentation are, in all these instances, the same. 


LECTURE LXXI. 


On THe Derivatives or FerMENTATIVE PRocESSES.—~ 
Alcohol.—Its Properties.— Exists in Wines. — Lactic 
Acid.— Production and Properties—Sulphuric Ether. 
—Its Distillation. — The Ethyle Series—Chloride.— 
Bromide.—WNitrate, §¢e—Cinanthic Ether. 

ALCOHOL (Hydrated Oxide of Ethyle) CsHeOs. 

By the distillation of wine, or any other fermented sac- 
charine juice, spirits of wine may be obtained. As first pre- 
pared, it contains a large quantity of water, which comes 
over withit. This product being rectified, and the first por- 
tion preserved, yields a spirit containing twelve to fifteen 
per cent. of water. By putting this into a retort with half 
its weight of quicklime, keeping the mixture a few days, 
and then distilling at a low temperature, absolute or an- 
hydrous alcohol is obtained. 

Anhydrous alcohol is a colorless liquid of a burning 
taste and pleasant odor. Its specific gravity, at 60° F., is 
0°795. It boils at 173° F., and at a still lower point if slight- 
_ ly diluted with water, though the boiling point rises if the 
water be in greater proportion. It has not been yet fro- 
zen. The specific gravity, also, varies with the amount of 
water present; and hence the purity of spirits of wine 
may be determined by ascertaining its density. Alcohol 
is very inflammable, burns with a pale blue flame, with 
the producton of carbonic acid gas and water. It is much 
used in chemical investigations as furnishing a lamp flame 
free from smoke, and as possessing an extensive range of 

How is alcohol procured? How may it be obtained anhydrous? What 


are its properties? How may the strength of spirits of wine be deter- 
mined? For what purposes is it used in chemistry? 


324 LACTIC ACID. 


solvent powers, acting upon resins, oils, and other bodies, 
which are not acted upon by water. 

The strong wines, such as port and sherry, contain from 
nineteen to twenty-five per cent. of alcohol; the light 
wines from twelve per cent. upward; and beer, porter, 
&c., from five to ten per cent. 

Lactic Acid Fermentation — We have already seen that 
vegetable juices as well as milk will, under certain cir- 
cumstances of temperature, yield, during fermentation, 
lactic acid instead of alcohol. This acid may, therefore, 
be made by dissolving a quantity of sugar of milk in milk, 
putting it in a warm place, and allowing it to turn sour 
spontaneously. <A part of the caseine of the milk here acts 
as the ferment, and as lactic acid is set free, it coagulates 
the rest and makes it insoluble. By the addition of car- 
bonate of soda, to neutralize the acid, this is prevented, and 
the ferment resuming its activity, produces more lactic 
acid. When, by this process, all the sugar is exhausted, 
the liquid is boiled, filtered, evaporated to dryness, and 
the lactate of soda dissolved out by hot alcohol. From 
this alcoholic solution the acid may be obtained by pre- 
cipitating the soda by sulphuric acid. 

Lactic Acid (C;H;0;+-HO) is obtained as asirupy solu- 
tion by concentrating in a vacuum over oil of vitriol. It is 
colorless, has a specific gravity of 1:215, is very sour, and 
soluble in water and alcohol. It yields a complete series 
of salts, most of which are soluble. Among these salts, 
the most interesting are those of lime and of zinc. 

Eruer—Sulphuric Ether— Oxide of Ethyle (C,H,0). 
—Lther is prepared by distilling equal weights of alcoho} 
and oil of vitriol, receiving the resulting vapor in a Lie- 
big’s condenser, adhe, as in Fig. 269, the condenser be- 
ing cooled by water from the reservoir, 2, flowing into the 
funnel, c, the waste passing into the vessel, 6, and the ether 
distilling into the bottle, e. The process is to be stopped 
as soon as the mixture begins to blacken. The first prod- 
uct may be rectified by redistillation from caustic potash. 

Ether is a colorless and limpid liquid, of a peculiar 
odor and hot taste. It boils at 96° F., and has not yet 


How much alcohol per cent. is contained in port, sherry, beer and ale? 
What is the process for obtaining lactic acid? What is its constitution ? 
What are its properties? How is ether made? What are the proper- 
ties of ether ? 


COMPOUNDS OF ETHYLE. 325 


\/ 


wl: A 


Stat 5 ate ee 
eae EES oe 
ee ie po 


r 
Ae TILT 


been frozen. Its specific gravity, at 60° F., is °720. It 
volatilizes with rapidity, and therefore produces cold. It 
is combustible, and burns with the evolution of much more 
light than alcohol. The specific gravity of its vapor is 
2:586. With oxygen or atmospheric alr it forms an ex- 
plosive mixture, and, kept in contact with air, it becomes 
acid from the production of acetic acid. It dissolves in 
alcohol in all proportions, but ten parts of water are re- 
quired to dissolve one of it; it also dissolves many fatty 
substances, and hence is of considerable use in organic 
chemistry. 

Ether is regarded as the oxide of an ideal compound 
radical, ethyle, C,H;, which gives rise to a series of other 


bodies. 3 
The Ethyle is 
Bthytes Cre 0. W.) 29 ooo eeide, 
Oxide.of ethyle, ... « «/ #4, ¢.=>. Ae QO, 
TEVOrubed ORIG. 0 \s. ee tae — Ae, O + HO. 
Chloride of etiyle’) Fete *. = er Cl 
Bromide en ros Aen 
Nitrate eg te oe pe eA) oe WN Oh, 
Hypomtrite, oS) Ss Ser ON Os, 
&e. Pada 


The oxide of ethyle, as has just been stated, is ether it- 
self, The hydrated oxide is alcohol. 


Is it soluble in water? What class of bodies does it dissolve? Of 
what substance is it an oxide ? 
E-r 


326 - COMPOUNDS OF ETHYLE. . 


Chloride of Ethyle—Hydrochloric Ether—may be made 
by saturating rectified spirits of wine with dry hydro- 
chloric acid gas, and distilling the result at a low tempera- 
ture, conducting the vapor through a bottle of warm wa- 
ter, and then condensing in a receiver surrounded by a 
freezing mixture. It is a colorless, volatile liquid, of a 
peculiar aromatic smell; the specific gravity is ‘874. It 
boils at 52°, and is not decomposed by nitrate of silver. 

Bromide of Ethyle (Hydrobromic Ether) and Iodide of 
Ethyl (Hydriodic Ether) are not of any importance ; and 
the same remark may be made as respects the sulphuret 
and the cyanide. 

Nitrate of Ethyle—Nitric Ether—may be made on the 
small scale by distilling equal weights of alcohol and nitric 
acid with a small quantity of nitrate of urea. The latter 
substance is used to prevent the nitric acid deoxydizing, 
and giving rise to the production of hyponitrite instead of 
nitrate of ethyle. Nitrate of ethyle is insoluble in water, 
has a density of 1:112, boils at 185°, and has a sweet 
taste. Its vapor explodes when heated. 

Fyponitrite of Ethyle—Nitrous Ether (AeO, NO;).— 
This ether may be made by passing the hyponitrous acid, 
disengaged from one part of starch and ten of nitric acid, 
through alcohol, diluted with half its weight of water and 
kept cold. It is a yellowish, aromatic liquid, having the 
odor of apples. It boils at 62° I’. Its density is -967. 
The sweet spirits of nitre is a solution of this ether with 
aldehyde and other substances in alcohol. 


Carbonate of Lithyle—Carbomc Ether (AeO, CO,)— 


made by the action of potassium on oxalic ether, and distill- | 


ation of the product with water. It floats on the surface of 
the distilled liquid, is an aromatic liquid, and boils at 259°. 

Oxalate of Kthyle—Oxalic Ether—prepared by distill- 
ing four parts of binoxalate of potash, five of sulphuric 
acid, and four of alcohol into a warm receiver. The 
product is washed with water to separate any alcohol 
or acid, and redistilled. It is an oily liquid, of an aro- 
matic odor; it boils at 353° F., and is slightly heavier than 
water. With an excess of ammonia it yields Oxamide and 


What is the true name of hydrochloric ether, and how is it prepared ? 
How is the nitrate of ethyle made? How is nitrous ether prepared, and 
what are its properties? How are carbonic ether, acetic ether, and for- 
mic ether made ? 


SULPHOVINIC ACID. 327 


alcohol. With a smaller proportion of ammonia and al- 
cohol it yields Oxamethane, C,H,NO,. 

Acetate of Ethyle—Acetic Ether (AeO, C,H,O,)—and 

Formate of Ethyle—Formic Ether (AeO, C,HO;)—are 
procured 1 in a similar manner with the foregoing, substi- 
tuting in one case acetate .of potash, and in the other 
formiate of soda. 

Ginanthic Ether (AeO, C\,H,;O,) is prepared from an 
oily liquid which passes over during the distillation of cer- 
tain wines. It has a powerful vinous odor, is a colorless 
liquid, specific gravity *862; it boils at 410° F., dissolves 
readily in alcohol, and gives their peculiar aroma to the 
wines in which it is found. From it cnanthic acid may 
be obtained by the successive action of potash and sul- 
phuric acid. It is an oily body, becoming a soft solid at 
55° F, 


LECTURE LXXII. 


Derivative Bopigs or ALcono..—Sulphovinic and Phos- 
phovine Acids.—Products of Sulphovinie Acid at Dif- 
ferent Bowling Points —The continuous Ether Process. 
—The continuous Olefiant Gas Process. — Dutch Li- 
quid.— Successive Substitutions of Chlorine in it— Heavy 
and Light Oil of Wine.—Sulphate of Carbyle and its 
derivative Acids. 


Sutpnovinic Acid—Bisulphate of Ethyle(C,H,O.2SO; 
+ HO).—A mixture of sulphuric acid with an equal weight 
of alcohol is to be heated to the boiling point, and then 
allowed to cool. It is then to be diluted with water and 
- neutralized with carbonate of baryta; the sulphate of ba- 
ryta subsides. The solution is then filtered, evaporated, 
and, when cold, the sulphovinate of baryta crystallizes. 
From this the sulphovinic acid may be obtained by pre- 
cipitating the baryta with dilute sulphuric acid, and evap- 
orating the resulting solution in vacuo. It is a sirupy 
liquid, of a sour taste, giving rise to a series of soluble 
salts, which decompose at the oe point, as will be pres- 
ently seen. : 


From what source is cenanthic ether derived? What is its relation to 
vinous bodies? How is sulphovinic acidmade? W hat is its composition? 


328 CONTINUOUS ETHER PROCESS. 


s 


Phosphovinic Acid (C,H,O, P O,;+2HO) is made on the 
same principles as the foregoing, phosphoric acid being 
substituted for sulphuric, and decomposing the resulting 
baryta salt in the same way. It is a sirupy liquid, of a 
sour taste, and dissolves in water, alcohol, and ether very 
readily. It is decomposed by heat. 

If sulphovinic acid be diluted so as to bring its boiling 
point below 260° F., it is resolved at that temperature 
chiefly into sulphuric acid and alcohol, which distills over. 

If the boiling point is from 260° F. to 310° F., the dis- 
tillation results chiefly in the production of hydrated sul- 
phuric acid and ether. 

If, by the addition of sulphuric acid, the boiling point 
is carried above 320° F., the action is more complex, but 
the chief product which .passes over is olefiant gas. 

The ordinary method of preparing ether is, therefore, 
obviously very disadvantageous, because it is only within 
a particular range of temperature that that. body is evolved. 
At first the low temperature yields alcohol, and as the 
heat rises, the mixture begins to blacken and olefiant gas 
to be evolved. 

To obviate these difficulties, a very beautiful process, 
the continuous process, has been introduced. It consists 
in taking a mixture of eight parts by weight of sulphuric 
acid and five of alcohol, specific gravity °834, the boiling 
point of which is about 300° F. This is brought to that 
temperature, and alcohol of the same density is allowed 
slowly to flow into the mixture, the boiling point being 
steadily kept as near 300° I’. as possible, and the mixture 
maintained in a state of violent ebullition. Water and 
ether distill over together, and may be passed through a 
Liebig’s condenser; they collect in the receiver in sepa- 
rate strata, or, if this does not take place at first, the ad- 
dition of a little water in the receiver insures it. 

In this manner a very large quantity of alcohol may be 
converted into ether and water by the action of a limited 
amount of sulphuric acid; and in a similar manner, by ad- 
justing the boiling point so as to be between 320° and 
330° F., olefiant gas may be continuously obtained. All, 
therefore, that is required, is to convey the alcoholic va- 


What is the composition and mode of preparation of phosphovinic acid ? 
What is the result of the exposure of sulphovinic acid at different boiling 
points? Describe the continuous process for the preparation of ether. 


SUBSTITUTIONS IN DUTCH LIQUID. 329 


por through a mixture of oil of vitriol with half its weight 
of water, which has the required boiling point. In this 
process the acid does not blacken, and it is therefore much 
more advantageous than that described for the preparation 
of olefiant gas in Lecture LIV. 

Chloride of Olefiant Gas—Dutch Liquid (CH,Cl,)— 
is prepared by mixing equal volumes of chlorine and ole- 
fiant gas in a large glass globe. It is a colorless and fra- 
grant liquid, soluble in alcohol and ether, but less so in 
water. It boils at 180° F’., and when acted on by a so- 
lution of caustic potash in alcohol, it yields chloride of 
potassium and a substance C,;C/, which, on being cooled 
by a freezing mixture, condenses into a liquid. This li- 
quid, brought in contact with chlorine, absorbs that sub- 
stance, and yields a new compound, C,;C/, which may 
again be decomposed by an alcoholic solution of potash 
into chloride of potassium and a new volatile body, 
Tt, Gl... 

There is an iodide and a bromide of olefiant gas, which 
possess a constitution analogous to the chloride. 

When chlorine gas is made to act upon Dutch hquid, 
three different substances may be successively formed by 
the gradual abstraction of hydrogen, and its equivalent 
substitution by chlorine. These substances are as follow: 


Dretch iquid er 2s. Adee. 
Cis) te a PoC gels: 
(Sates et cee Ga ie Cle. 
(Seyeeie eb aa Oe els. 


The first and second of these products are volatile li- 
quids, the third is the perchloride of carbon, in which it ap- 
pears that all the four atoms of hydrogen in the Dutch 
liquid have been removed, and their places occupied by 
-four atoms of chlorine. This perchloride of carbon is a 
white, crystalline body, soluble in alcohol and ether. Its 
melting point is 320° IF’. By passing its vapor through a 
red-hot porcelain tube, it is decomposed, yielding C,Cl, 
and free chlorine, and this again gives rise to subchloride 
of carbon, C,Cl,, by being passed through an ignited por- 
celain tube at a white heat. The former of these bodies 
is a colorless liquid, and the latter a silky solid. 

Heavy Oil of Wine (C,H,O, 2SO,) may be procured 

Describe the continuous process for preparing olefiant gas. How is 


Dutch liquid prepared? Whatis the nature of the series of bodies arising 
from the action of chlorine on it? 


E52 


330 OXYDATION OF ALCOHOL. 


by the destructive distillation of sulphovinate of lime, or 
by distilling two and a half parts of oil of vitriol and one 
of spirit of wine. It is a colorless liquid, heavier than 
water, and having an odor of peppermint. Boiled with 
water, it yields sulphovinic acid, and Light, or Sweet Oul 
of Wine,asubstance which, after standing a few days, de- 
posits white inodorous crystals of Htherine, C,H, ‘The 
residue, which still remains liquid, is Htherole, C,H,. It 
is a yellowish liquid, lighter than water, and soluble in 
wcohol and ether. 

Sulphate of Carbyle (C,H, 4S0O;) arises when the va- 
por of anhydrous sulphuric acid is absorbed by pure alco- 
hol. It is a white crystalline body. When dissolved in 
alcohol, and water added, the solution neutralized by car- 
bonate of baryta, filtered, concentrated, and then mixed 
with alcohol, the Ethionate of Baryta precipitates. This, 
when decomposed by dilute sulphuric acid, yields Hydra- 
ted Hthionic Acid, the constitution of which is C,H,O, 
4SO,-+2HO. Ethionic acid yields a series of salts, 
many of which can be obtained in crystals. On being 
boiled, solution of ethionic acid yields sulphuric acid and 
Isethionic, the peculiarity of which is, that it is isomeric 
with sulphovinic acid, both containing C,H,O, 2SO; + 
HO. . . 


LECTURE LXXIiTl, 


OxypaTion or Atconot.—The Acetyle Group.—Alde- 
hyde.—Its Preparation and Properties.— Aldehydic 
Acid.— Davy’s Flameless Lamp.—Acetal produced by 
Platinum Black.— Acetic Acid, Production of.— Na- 
ture of the Change from Alcohol to Acetic Acid.—Salts 
of Acetic Acid. 

Ir has been already stated (Lecture LXXI.), that when 
alcohol is burned in contact with oxygen gas or atmos- 


pheric air, the sole products of the combustion are car- 
bonic acid gas and water. But when the oxydation is 


Under what circumstances does the heavy oil of wine form? How is 
sweet oil of wine prepared? What are etherine and etherole? When 
the vapor of anhydrous sulphuric acid is passed into pure alcohol, what is 
the result? How are ethionic and isethionic acids prepared? 


ALDEHYDE. sol 


partial, the hydrogen is removed by preference, and a new 
series of bodies is the result, designated as 


The Acetyle Series. 


enous Crate le ie. hr ai ct) s Se Ae, 

Oxide of acetyle : a Ael, 
Hydrated oxide of acetyle (aldehy de) . .=AcO + HO. 
Acetylous acid fergie dic a oss soe ACOme-taii Gh, 
Acetic acid . a; = AcO; + HO. 


Acetyle is an eal Badys aiffertnn fran ethyle by con- 
taining only three atoms of hydrogen instead of five. Its 
oxide, also, has not yet been insulated. 

fal ydrated Oxide of Acetyle—Aldehyde—may be ob- 
tained by distilling two parts of the compound of aldehyde 
and ammonia, dissolved in two parts of water, with a mix- 
- ture of three of oil of vitriol and four of water, and redis- 
tilling the product from chloride of calcium at a low tem- 
perature. It is a colorless liquid, of a suffocating odor. 
Its density is -790, its boiling point 72° F. It is soluble 
in water and alcohol. It slowly oxydizes in the air, and 
more rapidly under the influence of the black powder of 
platinum, producing acetic acid. Heated with caustic 
potash, it yields aldehyde resin, a brown body of a resin- 
ous aspect. Aldehyde has received its name from the 
circumstance that it contains the elements of alcohol mz- 
nus two atoms of hydrogen (Alcohol Dehydrogenatus). 

When pure aldehyde is kept for a length of time at 
32° T°. in a close vessel, it yields E/aldehyde, a substance 
isomeric with itself, but possessing different properties, 
the specific gravity of its vapor, for example, being three 
times that of the vapor of aldehyde. Fig. 270. 
From it there is also produced, at com- 
mon temperatures, a second isomeric 
body, Metaldehyde. 

Aldehydic Acid may be obtained by 
digesting oxide of silver with alde- 
hyde, and precipitating the metal with 
sulphureted hydrogen. It contains 
one atom of oxygen less than acetic 
acid, and is one of the products of the 
slow combustion of ether in Davy’s = 
flameless lamp, which may be made ~ 


What is acetyle? How is aldehyde prepared? What are its proper- 
ties? From what is its name derived? Under what circumstances do 
elaldehyde and metaldehyde form? What is Davy’s flameless lamp ? 


332 PREPARATION OF VINEGAR. 


by putting a small quantity of ether in a jar (fg. 270, 
page 331), and suspending in the vapor, as it mixes with 
atmospheric air, a coil of platina wire which has recently 
been ignited, The wire remains incandescent as long as 
any ether is present. The same result is obtained by 
putting a spiral of platina wire, or a ball of spongy pla- 
tina, over the wick of a spirit lamp, the lamp being lighted 
for a short time, and then blown out; the platinum: con- 
tinues incandescent, evolving a peculiarly acrid vapor. 
Acetal (C,H,O;), containing the elements of ether and 
aldehyde, is produced by the oxydation of vapor of alco- 
hol by black powder of platinum, the alcohol being placed 
in a jar, with moistened platinum black in a capsule above 
it. In the course of several days the alcohol will be 
found to have become sour; it is then to be neutralized 
with chalk and distilled. Chloride of calcium separates 
an oily liquid from the distilled product. This, on being 
distilled at a temperature of 200° F., yields acetal. It is 
a colorless and aromatic liquid, lighter than water, and 
boiling at 203° I’. It yields, under the influence of an 


alcoholic solution of caustic potash, by absorbing oxygen | 


from the air, resin of aldehyde. 

Acetic Acid —Py yroligneous Acid— Vinegar (C,H,;0;+ 
4TO).—When dilute alcohol is dropped on platina black, 
oxydation takes place, and the vapors of acetic acid are 

Fig. 271. formed. On the large scale it is also 

[tae = i formed by allowing a mixture of alcohol, 


= water, and a small quantity of yeast, 30, 
weg: ee i : : 

Sore Fig. 271, to flow over wood shavings 
which have been steeped in vinegar con- 
tained in a barrel through which atmos- 
pheric air is allowed to circulate by the 
apertures ccc. The temperature rises, 
and the acetification goes on with rapid- 
ity, the product being collected in the re- 
ceiver, d. Vinegar, also, is formed by the spontaneous 
souring of wines or beer containing ferment, and kept in 
a cask to which atmospheric air has access. During the 
destructive distillation of dry wood, acetic acid (hence 


Mention some of its products. What is the constitution of acetal? 
How may it be prepared by platinum black? Mention some of the differ- 
_ ent methods by which acetic acid may be made. Why is it sometimes 
called pyroligneous acid ? 


ACETIC ACID. 3833 


called pyroligneous acid) in an impure state is found 
among the products. 

The strongest acetic acid may be made by distilling 
powdered anhydrous acetate of soda with three times its 
weight of oil of vitriol. The product is then re-distilled, 
and exposed to a low temperature, when crystals of hy- 
drated acetic acid form; the fluid portion is poured off, 
and the crystals suffered to melt. It is a colorless liquid, 
which crystallizes below 60° F.; has a very pungent odor, 
and, placed on the skin, blisters it; boils at 248° F’., the 
vapor being inflammable. It dissolves in water, alcohol, 
and ether; and in a less pure state, as vinegar, its taste, 
odor, and applications are well known. If its constitution 
be compared with that of alcohol, 


PRIGOHOs ek a oe Pa CdAeOs 
Acentetid jnen tS es lo OghOsg 


it is seen to differ from that substance in the circumstance 
that two hydrogen atoms have been removed from the al- 
cohol, and their places taken by two oxygen atoms. Hence 
the various processes for its production are easily ex- 
plained. Acetic acid gives rise to several important salts. 

Acetate of Potash (ILO, C,H, O;) is obtained by neutraliz- 
ing acetic acid with carbonate of potash, evaporating to 
dryness, and fusing. This salt is very deliquescent, and 
has an alkaline reaction. 

Acetate of Soda is made on the large scale by saturating 
the impure pyroligneous acid formed in the destructive 
distillation of wood, with lime, and then decomposing the 
acetate of lime with sulphate of soda. The sulphate of 
lime precipitates, thesolution being crystallized, and the 
crystals subsequently purified by draining, fusing, solu- 


_ tion, and re-crystallization. ‘The crystals effloresce in the 


air, and are soluble in water and alcohol. 

Acetate of Ammonia—Spirit of Mindererus—The solu- 
tion is made by saturating acetic acid with carbonate of 
ammonia, and the solid by distilling acetate of lime and 
hydrochlorate of ammonia; the acetate of ammonia passes 
over, and chloride of calcium is left. 

Acetate of Alumina is made by the decomposition of a 


—_— 


What change does alcohol undergo in passing into acetic acid? Mene 
tion some of the more important salts of acetic acid. How is the acetate 
of soda made? What is the spirit of Mindererus ? 


334 SALTS OF ACETIC ACID. 


solution of alum by acetate of lead. It is much used by 
dyers as a mordant. 

Acetates of Lead.—I|st. Neutral Acetate (Sugar of Lead) 
may be made by dissolving litharge in acetic acid. It 
occurs in colorless prismatic crystals, and also in crys- 
talline masses. It has a sweetish, astringent taste, from 
which its commercial name is derived. It is soluble in 
about its own weight of cold water. The crystals efflo- 
resce in the air. 2d. Subacetates of Lead—Sesquibasic 
Acetate—is formed by partially decomposing the neutral 
acetate by heat. Its solution is known as Goulard’s Wa- 
ter. ‘Two other subacetates may be made by the action 
of ammonia on the neutral salt. Their solutions have an 
alkaline reaction, absorb carbonic acid from the air, and 
give rise to a precipitate of the basic carbonate. 

Acetates of Copper.—\st. Neutral Acetate — Distilled 
Verdigris — made by dissolving verdigris in hot acetic 
acid. On cooling, it yields green crystals, soluble both 
in water and alcohol. It is used asapaint. 2d. Bibasic 
Acetates of Copper— Verdigris—may be made by the ac- 
tion of vinegar and air conjointly on metallic copper. 
Verdigris is a mixture of several acetates, one of which 
may be obtained by digesting it in warm water; a second 
arises on boiling this; the insoluble residue of the verdigris 
contains a third. 


LECTURE LXXIV. 


Derivatives oF -AcETYLE—Tue KakopyLe Grovur.— 
Chloracetic Acid.—Acetone.—Chloral and Heavy Mu- 
riatic Ether.—Substitutions of Chlorine in Light Mu- 
riatic Ether.—Sulphur-alcohol—Its Relations to Mer- 
cury.—Xanthic Acid.—The Kakodyle Group.— Oxide. 
—Chloride—Kakodylic Acid. 


Cuioracetic Acid (C,HO,Cl;)—This remarkable body 
is formed when a small quantity of crystallized acetic 
acid is exposed to the sunshine in a jar-full of chlorine 
gas. ‘The crystals which form on the inside of the vessel 


For what purpose is acetate of alumina used? What varieties of ace- 
tate of lead are there, and how are they formed? What are the varieties 
of acetate of copper? How is chloracetic acid made ? 


DERIVATIVES OF ACETYLE. 335 


are to be dissolved in water, and the solution evaporated 
in vacuo with capsules containing caustic potash and oil 
of vitriol. A little oxalic acid is first deposited, and then 
the chloracetic acid crystallizes as a colorless and deli- 
quescent body, with a powerfully acid taste, and capable 
of corroding the skin. It melts at 115° F’.,.and boils at 
390°. By comparing its constitution with that of acetic 
acid, it will be seen that in its formation three atoms of 
chlorine have been substituted for three of hydrogen. It 
yields an extensive series of salts. 

Acetone—Pyroacetic Spirit (C,H,0)—may be made by 
passing acetic acid vapor through a red-hot iron tube, 
or by the distillation of dry acetate of lead. It is a lim- 

id, colorless, and volatile liquid, boiling at 132°, burns 
with a bright flame, and is soluble in water and alcohol. 
Nordhausen oil of vitriol, distilled with acetone, abstracts 
from it one atom of water, yielding an oily body, the con- 
stitution of which is C,H; it is lighter than water, and 
“has an odor of garlic. 

Sir R. Kane considers acetone to be the hydrated ox- 
ide of an ideal radical, Mesztyle, C,H;, and has been able 
to produce the oxide and chloride of mesityle. Zeise also 
discovered a compound consisting of the oxide of mesityle 
and bichloride of platinum. 

Cutorat (C,HC/,0,)—When dry chlorine is passed 
into anhydrous alcohol, and the action finished by the aid 
of heat, hydrochloric acid is produced ; and on its ceasing 
to appear, if the product be agitated with three times its 
volume of oil of vitriol, and the mixture warmed, an oily 
liquid floats on the acid: this is chloral. It may be puri- 
fied by successive distillation from oil of vitriol and quick- 

-lime. Itis an oily, colorless liquid, which causes a flow of 
tears, leaves a transient greasy stain upon paper, has a 
density of 1:502, boils at 201°, is soluble in water and al- 
cohol; it yields no precipitate with nitrate of silver. When 
kept for a length of time in a sealed tube, it spontaneous- 
ly becomes a white, solid, insoluble chloral. In this con- 
dition it is little soluble in water, and reverts to its other 
state by being warmed. . 

If chlorine acts on alcohol containing water, heavy Mu- 


What is the relationship between acetic and chloracetic acid? What 
is the mode of preparing pyroacetic spirit? What is mesityle? What 
is chloral? Under what circumstances does insoluble chloral form? 


336 SULPHUR-ALCOHOL. 


riatic Ether is formed. It is a colorless and volatile 
liquid, 

The action of chlorine upon common ether, and also on 
the compound ethers, is very interesting. It consists in 
the gradual removal of hydrogen, chlorine being substi- 
tuted for it. This, in many instances in which the aid of 
the sunlight is regen to, terminates in the entire re- 
moval of the hydrogen. Inthe compound ethers it is the 
basic hydrogen which is removed, while that of the acid 
escapes, as in the case of chlor eda acetic and chlorureted 
formic ethers. When the vapor of light hydrochloric 
ether is acted upon by chlorine gas, a complete series of 
compounds may be obtained, the hydrogen eventually 


disappearing : 
Hydrochloric ether . . », pnOplleCes 
Monochlorureted hydrochloric ether vo MC ida Gia 
Bichlorureted .) » OgtigClg: 
TY'richlorureted - os + » CRAZE: 
Quadrichlorureted us: a on bs Mtg oles 
Perchloride of carbon . . . Wi Cig pakke s 


furnishing, therefore, a very striking instance of the doc- 
trine of substitution, 

Mercaptan—Sulphur-alcohol (C,H,S,)—is prepared by 
saturating a solution of caustic potash, specific gravity 
1:3, with “sulphureted hydrogen, and distilling it with an 
equal volume of sulphovinate of lime of the same density. 
It passes over with water, on the surface of which it 
floats as a colorless liquid, specific gravity ‘842, soluble 
in alcohol. It boils at 97°, smells like onions, and burns 
with a blue flame. Mercaptan corresponds to alcohol in 
which all the oxygen has been replaced by sulphur; but 
in its action on metallic oxides it answers to the hydruret 
of a compound radical, C,H,;S,. Thus, with peroxide of 
mercury, it forms a mercaptide with the production of 
water; and this may be decomposed by sulphureted hy- 
drogen, sulphuret of mercury subsiding, and mercaptan 
being reproduced. Mercaptan derives is name from its 
strong afhnity for mercury (Mercurium Captans). 

Xanthic Aed ( C;,H;S,O0 + HO).—Hydrate of potash is 
to be dissolved in twelve parts of alcohol, specific gravity 
800, and bisulphuret of carbon dropped into the solution 


—— 


Describe the successive action of chlorine upon ether. What remark- 
able qualities does mercaptan possess? How is it prepared? From 
what is its name derived? What is the process for preparing xanthic 
acid? 


KAKODYLE. 337 


until it ceases to have an alkaline reaction. On cooling to 
ZeTO, the xanthate of potash crystallizes: it is to be dried 
in vacuo. It is soluble in water and alcohol, but not in 
ether; and from it xanthic acid may be procured by the 
action of dilute hydrochloric acid. Xanthic acid is an 
oily liquid, heavier than water, which first reddens and 
then bleaches litmus paper. At 75° it is decomposed 
into alcohol and bisulphuret of carbon. It is also decom- © 
posed by the action of the air. 

Kakopyte (C,H,As = Kd) is a compound radical, 
which gives rise to’ an extensive group of bodies, in which 
it acts the part of a metal. 

The tet aoe 


Kakodyle, CsHsAs.. . . ape 8. © 
Oxide of kakodyle se: 5 ics) 0 wl + s' # FR REO, 
Chloride s Sings Ssibe > a se tte, « thee Ae ee 
Todide « JPG Uy MIS a 1 ee ae 
Sulphuret “ shy. JSR t vila. Gi Gal See Ae 
&c. &c. 


Kakodyle may be obtained by decomposing the chlo- 
ride of kakodyle with metallic zinc in an apparatus filled 
with carbonic acid gas, and may be purified by re-distil- 
lation from zinc, similar precautions being taken to ex- 
clude atmospheric air. It is a colorless liquid, of a pow- 
erful odor, taking fire on the contact of air, oxygen gas, 
or chlorine; boils at 338°, crystallizes at 21°, and is de- 
composed by a red heat into olefiant gas, light carbureted 
hydrogen, and arsenic. 

Oxide of Kakodyle—Alkarsine—Cadet’s Fuming Liquor 
—is prepared by the distillation of acetate of potash and 
arsenious acid, receiving the products in an ice-cold vessel 
the temperature being finally carried to a red heat. The 
oxide comes over in an impure state, sinking to the bot- 
tom of the other products. It is to be decanted, washed 
with water, boiled, and then distilled in a vessel full of 
hydrogen from hydrate of potash. It is a colorless li- 
quid, specific gravity 1:462, boils at 300°, and solidifies at - 
9°; is sparingly soluble in water, but more so in alcohol ; 
is excessively poisonous, possessing a concentrated smell 
like garlic. Heated in the air, it burns, producing car- 
bonic acid, water, and arsenious acid. 

Chloride of Kakodyle may be procured by the action of 

~ What is its action on litmus paper? What is rages Pied How may it 


be isolated? What are alkarsine and Cadet’s fuming liquor? How is it 
prepared, and what are its properties 7? 


F 


338 THE WOOD-SPIRIT GROUP. 


a dilute solution of corrosive sublimate on a dilute alco 
holic solution of oxide of kakodyle; a white precipitate 
falls, which, distilled with strong hydrochloric acid, yields 
corrosive sublimate, water, and the chloride of kakodyle 
passes over. When purified by chloride of calcium, and 
distilled in an atmosphere of carbonic acid, it is a color- 
less liquid, of a dreadful odor, heavier than water, and in- 
soluble therein, but soluble in alcohol. It is very poison- 
ous. It boils at about 212°, the vapor taking fire in the 
air. 

Kakodylic Acid—Aleargen (Kd .O;)—may be made by 
the action of oxide of mercury upon oxide of kakodyle un- 
der the surface of water, at a low temperature. Kakodylic 
acid forms crystals which deliquesce in the air, are soluble 
in water and alcohol, but not inether. Itis not acted upon 
by oxydizing agents, such as nitric acid, but is reduced to 
oxide of kakodyle by several deoxydizing bodies. It is 
not poisonous. 

Kakodyle furnishes a complete series of bodies: the 
iodide, sulphuret, cyanide, and a substance isomeric with 
the oxide, which has the name of parakakodylic oxide. 


LECTURE LXXV. 


Tur Woop-Sririt Grour.—Methyle.— Its Oxide and Hy- 
drated Oxide.—Salts of Methyle—Formic Acid, natu- 
ral and artificial Production of —Derivatives of Wood 
Spirit —Substitutions of Chlorine in Oxide of Methyle— 
Substitutions in Chloride of Methyle. 


In the destructive distillation of wood in the prepara- 
tion of pyroligneous acid, there passes over a body to 
which the name of wood spirit has been given. This is 
the hydrated oxide, or alcohol of an ideal compound. rad- 
ical, passing under the name of methyle. 


The Methyle Group. 


Methyle, Coss. » » == Me, 
Oxide of methyle ... .=MeO 
Hydrated oxide . . . . .=MeO-+ HO. 
Whioride if Giant Mets. z= eC. 

&e. &e. 


Hee ee a a a a a ae aaa) 

What is the process for preparing the chloride of kakodyle? What are 
its properties? What is the constitution of alcargen? Under what cir- 
cumstances is wood spirit produced? Whatis its ideal compound radical? 


COMPOUNDS OF METHYLE. 339 


Oxide of Methyle— Methylic Ether— Wood Ether 
(C,H,O).—This substance is made from the hydrated ox- 
ide on the same principle that ether is obtained from al- 
cohol: one part of wood spirit and four of oil of vitriol 
being heated in a flask, the vapor is passed through a small 
quantity of caustic potash solution, and received at the mer- 
curial trough. It is a permanently elastic gas, colorless, 
and has a specific gravity of 1°617, burns with a pale flame, 
is very soluble in water, which takes up thirty-three times 
its volume of it, and yields it unchanged when heated. 

Hydrated Oxide of Methyle— Wood Spirit—Pyroxylic 
Spirit—may be separated from crude wood vinegar by dis- 
tillation. It passes over with the first portions along with 
a little acid, which, being neutralized with hydrate of lime, 
the wood spirit may be separated from the oil which floats 
on its surface, and redistilled. The product thus obtained 
may be rectified in the same manner as common alcohol, 
and rendered anhydrous by quicklime. It is then a color- 
less liquid, of a hot taste and peculiar smell. It boils at 
152°, and has a specific gravity of ‘798 at 68°. It is sol- 
uble in water, dissolves resins and oils, and may be burn- 
ed like spirit of wine. It then exhales a peculiar odor. 

Chloride of Methyle (MeCl) may be made from the re- 
action of sulphuric acid upon common salt and wood 
spirit. It is a colorless gas, which may be collected over 
water; has a density of 1°731. It has a peculiar odor, is 
inflammable, and may be decomposed by passing through 
a red-hot tube. 

Sulphate of Oxide of Methyle (MeO, SO;) may be pre- 
pared by distilling one part of wood spirit with eight or 
ten of oil of vitriol; the product is to be washed with 
water, and redistilled from caustic baryta. It is an oily, 
neutral liquid, smelling like garlic; specific gravity 1:324. 
It boils at 370°. It is not soluble in water, but is decom- 
posed by that liquid, especially at the boiling temperature, 
into sulphomethylic acid and hydrated oxide of methyle. 
It is to be observed, that in the series of wine alcohol 
there is no compound corresponding to this. 


Nitrate of Oxide of Methyle (MeO, NO,) is obtained by 


~ How i is the oxide of methyle prepared, and what is its form? What is 
the constitution of pyroxylic spirit? What are its properties, and for 
what purposes may it be used? How is the chloride of methyle prepar- 


ed? In the wine series, is there any compound analogous to sulphate of 


oxide of methyle ? 


. 


340 FORMIC ACID. 


the action of a mixture of wood spirit and oil of vitriol 
upon nitrate of potash. It is a colorless liquid, heavier 
than water; boils at 150°; burns with a yellow flame. 
Its vapor explodes when heated. In a solution of caustic 
potash, it decomposes into nitrate of potash and wood 
spirit. 

Oxalate of Oxide of *Methyle (MeO, C,O,) is made by 
distilling oxalic acid, wood spirit, and oil of vitriol. The 
liquid which is collected is allowed to evaporate; it 
yields crystals of the oxalate. When pure, it is colorless ; 
melts at 124°, and boils at 322°. It is decomposed by 
hot water into oxalic acid and wood spirit, by solution of 
ammonia into oxamide and wood spirit. 

Sulphomethylic Acid (MeO, 2SO, + HO), the com- 
pound corresponding to sulphovinic acid, and prepared 
in the same way, by substituting wood spirit for alcohol. 
It is thus procured as a sirup or in small crystals, solu- 
ble in water and alcohol. Itis an instable body, and pos- 
sesses many analogies with sulphovinic acid. 

Formic Acid (C,HO, + HO).—This acid, in the wood- 
spirit series, is the analogue of acetic acid in the alcohol 
series. It may be procured on principles similar to those 
involved in the preparation of acetic acid, as by the grad- 
ual oxydation of the vapor of wood spirit in the air under 
the influence of black platinum. In a dilute state it may 
be prepared by distilling one part of sugar, three of per- 
oxide of manganese, and two of water, with three parts 
of sulphuric acid, diluted with an equal weight of wa- 
ter. The liquid which distills is to be neutralized by 
carbonate of soda, purified by animal charcoal, and redis- 
tilled along with sulphuric acid. It occurs naturally in 
the bodies of red ants, and hence has obtained the name 
of formic acid. From the distillation of those animals it 
was originally procured. 

Anhydrous formic acid (C,HO;) obviously contains 
the elements of two atoms of carbonic oxide and one of 
water. It yields two hydrates, respectively containing 
one and two atoms of water. The first, for which the 
formula has already been given, is procured by the ac- 


‘- How is the nitrate obtained, and what are its properties? Describe the 
preparation of the oxalate and of sulpho-methylic acid. What is the con- 
stitution of formic acid? How is it procured? From what circumstance 
is its name derived? What are its properties? 


DERIVATIVES OF METHYLE. 341 


tion of sulphureted hydrogen on formiate of lead. Itis a 
colorless liquid, of a strong odor; boils at 212°, and crys- 
tallizes below 32°. It is inflammable, and has a specific 
gravity of 1:235. It blisters the skin. Formic acid yields 
a complete series of salts. 

Chloroform (C,HCi;) is made by distilling wood spirit 
with a solution of chloride of lime. It is a colorless liquid ; 
specific gravity 1:48; boils at 141°. It burns with a 
green flame, and is decomposed by an alcoholic solution 
of potash into chloride of potassium and formiate of pot- 
ash. The relationship between formic acid and chloro- 
form is obvious: it consists in the substitution of three 
atoms of chlorine for three of oxygen. ‘There are also 
two analogous compounds : 


Brommortiy 4.5) +46 us) > CeltprTa. 
leddfertr) siP ee ces oe et Cony: 


Formomethylal (C;H,O,) is prepared by distilling wood 
spirit, oxide of manganese, and dilute sulphuric acid. On 
saturating the product with potash, formomethylal sepa- 
rates as a colorless oily liquid: specific gravity °855 ; 
boils at 107°, and soluble in water. 

Methyle-mercaptan— F ormed as the common mercap- 
tan, by substituting sulphomethylate of potash for sulpho- 
vinate of lime. It is analogous to common mercaptan. 

When chlorine is made to act on the oxide of methyle 
at common temperatures, it removes one of the hydrogen 
atoms ; and by continuing the action, a second may be 
taken away, and the process of substitution, as shown in 
the following series, may be carried so far as to end in the 
removal of oxygen and the production of chloride of 
carbon. 


Ozxidetofimethylev.. he 8 ee CL AO: 
1 Be. cubiatitation steele tha, oh AalGells OnE 
2d Me ae Ps UH IY, 0 
3d i Se QO EE Rte SRE Ele Sere tee. 
4th “t (chloride of carbon) . C', Cl,. 
Other methylic compounds furnish similar series, thus : 
Chioride’of methyle ..) 2. Si «a C5, CT. 
TEPC TS eas 61 one ree wpe meee Ow Fa a A 
2d ie chloroform) ..~. . 4» GsH Cl. 
3d ¢ chloride of carbon) . .C, Cl,. 


How is chloroform obtained? What is the process for preparing for- 
momethylal? Describe the series of substitutions of chlorine on the oxide 
ofmethyle. Describe the analogous le aac with chloride of methyle ? 


F 2 


342 | FUSEL OIL. 


LECTURE LXXVI. 


Tue Potato Om Grovup.— Fusel Oil. — Chloride of 
Amyle.— Sulphamylic Acid.— Amilen.— Relations of 
Valerianic Acid. 

Tue BenzyLte Groure.—Oil of Bitter Almonds.—Benzovc 
Acid.—Sulphobenzoic Acid.—Chloride of Benzyle.— 
Benzamide. 

In the distillation of brandy from potatoes, a volatile 
oil passes over. It is regarded as the hydrated oxide of 
an ideal compound radical, which passes under the name 
of Amyle, having the constitution C,)f),. 

The Potato Oil Group. 


Amyli, Ciolits’ #4 > peage > wen ie Bae ae 
Amyle ether . . ke pale te es ea 
Amyle alcohol (potato oil) Ol Fh ae lO BO: 
Chioride-ofamyle:. iis) an. wt se AQgCl 

&c. &c. 
Amilen . . eet ee Lei tice 
Valerianic acid . . . . . . CioHoOs. 


Of these, amyle and its oxide, amyle-ether, are ideal. 

Hydrated Oxide of Amyle—Amyle Alcohol—Potato Ou 
—Fusel Oil ( C,,H,, 0+ HO).—This substance passes over 
toward the end of the first distillation of potato spirit, and 
communicates to it a milky aspect. On standing, it floats 
on the surface, and may be purified by washing with wa- 
ter, drying with chloride of calcium, and redistillation. 
It is a fluid oil of a suffocating odor, which acts power- 
fully on the animal system. Its specific gravity is ‘818; 
it boils at 269°. 

Chloride of Amyle (AyilCl) is made by distilling equal 
weights of potato oil and perchloride of phosphorus, wash- 
ing with potash water, and redistilling from chloride 
of calcium. It is an aromatic liquid, boils at 215°, and 
burns with a green flame. Under the influence of sun- 
shine, eight of its hydrogen atoms may be removed, eight 
chlorine atoms being substituted for them, C,,f,, CZ yield- 
ing O,,—H;Cl,, forming chlorureted chloride of amyle. 


What is the imaginary radical of the potato oil group? What are the 
nature and relations of fusel oil? What are the properties of the chloride 
of amyle ? 


VALERIANIC ACID. 343 


The Jodide and Bromide of Amyle are compounds anal- 
ogous to the chloride. 

Acetate of Oxide of Amyle is obtained by distilling ace- 
tate of potash, potato oil, and sulphuric acid. It is a col- 
orless liquid, which boils at 257°, 

Sulphamilic Acid (AylO, 2SO,H-+ O) is generated 
when sulphuric acid is made to act on an equal weight of | 
potato oil. From this, by the successive action of car- 
bonate of baryta and sulphuric acid, it may be procured 
by operating on the same principles as for sulphovinic 
acid, to which, both in constitution and properties, it is 
the analogue. It is a sirupy or crystalline body, and is 
decomposed by ebullition into potato oil and sulphuric 
acid. 

Amilen (C\>H,) is obtained by the action of anhydrous 
phosphoric acid on potato oil; it is an oily liquid which 
boils at 320°. In constitution and position it, therefore, 
occupies, in the amyle series, the same situation that ole- 
fiant gas does for the wine alcohol series, and, indeed, is 
isomeric with that body. 

Valerianice Acid (C,H, O,) bears the same relation to det 
amyle group which acetic acid does to the wine alcohol 
group, or formic acid to the wood spirit group. It is 
formed when warm potato oil is dropped on platinum 
black in contact with the air. It occurs naturally in the 
root of the Valeriana Officinalis, but is best made by heat- 
ing potato oil in a flask, with a mixture of quicklime and 
hydrate of potash, for several hours at a temperature of 
4002. The white residue is immersed in cold water, and 
distilled with a slight ,excess of sulphuric acid, so as to 
drive off hydrated valerianic acid and water. It is a col- 
orless oil of an acid taste, combustible, and boiling at 3479. 
When acted upon by chlorine in the dark, and the action 
aided by heat, it gives rise to Chlorovalerisic Acid (C,H; 
‘Cl,0; + HO), in which there has been a removal of three 
hydrogen atoms and a substitution of three of chlorine. 
Under the influence of the sunshine, by the same process, 
another hydrogen atom is removed, and Chlorovalerosic 


Acid forms, its constitution being C,,—H;Cl,0,; + HO. 


” To what substance is sulphamilic acid analogous? What relation is 
there between amilen and olefiant gas? What is the relation between 
acetic and valerianic acids? From what natural source may the latter be 
derived? How is it made artificially? What is the successive action of 
chlorine upon it ? : 


344 THE BENZYLE GROUP. 


The Benzyle Group. 


Benzyle, CiuHsO2 . - - . - J iy SE ee 
Hydruret ofbenzyle + ..... 3. . . = B2z-E HH. 
Oxide of benzyle (benzoic acid) . . . . =Bz-+O. 
Chioride +. f 6 6 be ee et te = BC 
&e. &e. 


Of this series, benzyle, the radical, is an ideal body. [¢ 
is a radical which discharges the functions of a metallic 
body, giving rise to oxides, chlorides, iodides, &c., as the 
table shows. 

Hydruret of Benzyle—Oul of Bitter Almonds (Bz H)—is 
obtained by the distillation of bitter almonds, from which 
the fixed oil has been expressed, with water, and arises 
from the action of the water upon Amygdaline contained 
in the seed. It may be purified by distillation from pro- 
tochloride of iron with hydrate of lime in excess, and is a 
colorless liquid of an agreeable odor, slightly heavier than 
water, and also slightly soluble therein, but very soluble 
in alechol and ether. It boils at 356°. In the air it pass- 
es into benzoic acid by absorbing oxygen. 

Oxide of Benzyle—Benzoie Acid (BzO + #O).—This 
acid is obtained by sublimation from gum benzoin, that 
substance being placed in a shallow vessel, over the top 
of which a cover of filtering paper is pasted, and this cov- 
ered by a taller cylinder of stouter paper. On heating, 
the vapors pass through the filtering paper, and, condens- 
ing in feathery crystals im the space above, fall down upon 
the paper and are retained by it. A better method is to 
boil a mixture of the gum with hydrate of lime, filter, 
concentrate the solution, add hydrochloric acid, and the 
benzoic acid crystallizes inthm plates on cooling. Itmay 
be subsequently sublimed. When pure it has no odor. 
It melts at 212°, and boils at 462°. Its vapor excites 
coughing. It 1s much more soluble in hot than in cold 
water. It forms a series of salts, and is sometimes used 
for the separation of iron from other metals. 

Sulphobenzoic Acid (€,,H;O;, SO; + 2HO), a bibasic 
acid, formed by the action of anhydrous sulphuric acid 
upon benzoic acid, the mass being dissolved in water and ~ 
neutralized by carbonate of baryta. On filtering, and add- 


What is the radical of the benzyle series? What is oil of bitter al- 
monds? From what substance does it arise? What is benzoic acid? 
By what processes may it be prepared? What is the process for pre- 
paring sulphobenzoic acid ? 


DERIVATIVES OF BENZYLE. 345 


ing hydrochloric acid to the hot solution, on cooling the 
sulphobenzoate of baryta crystallizes, which may be de- 
composed by dilute sulphuric acid. It is a white crystal- 
line mass. 

Chloride of Benzyle (BzCl).— When chlorine gas is 
passed through oil of bitter almonds, hydrochloric acid is 
formed, and, after expelling the excess of chlorine by heat, 
chloride of benzyle remains. It is a colorless liquid, of 
a disagreeable odor, heavier than water, combustible, and 
decomposed by boiling water into benzoic and hydrochlo- 
ric acids. 

Benzamide (C,,H,NO,) is formed by the action of chlo- 
ride of benzyle on dry ammonia, the hydrochlorate of am- 
raonia being removed from the resulting white mass by 
cold water. From a solution in boiling water, the ben- 
zamide crystallizes. It melts at 239°. It corresponds 
in its chemical relations to oxamide. 

Hydrobenzamide (C,.H,;,.N,), made by the action of pure 
oil of bitter almonds on solution of ammonia, the product 
being washed with ether, and from its alcoholic solution 
this substance crystallizes; but when impure almond oil 
is employed, three other compounds may be obtained: 
they are benzhydramide, azobenzoyle, and nitrobenzoyle. 


LECTURE LXXVII. 


Tue SALICYLE AND CINNAMYLE Groups.—Benzoine, Ben- 
zone, Benzine-—Hippuric Acid.— T uE SavicyLe Group. 
—Artificial Formation of: Ou of Spirea.— Compounds 
of Salicyle—Melanic Acid.—'Tur CINNAMYLE Group. 
— Compounds of Cinnamyle. 


Benzoine (C,,H,O,), a body isomeric with bitter al- 
mond oil. It is found in the residue after purifying that 
oil from hydrocyanic acid by distillation from lime and 
oxide of iron, and may be obtained by dissolving out those 
bodies by hydrochloric acid. It crystallizes from an alco- 
holic solution, on cooling, in colorless crystals, which melt 
at 248°. It dissolves in an alcoholic solution of caustic 


How is the chloride of ‘benzyle made? How are benzamide and hydro: 
eller o formed? What relation does benzoine bear to oil of bitter 
almonds | 


346 DERIVATIVES OF BENZYLE. 


potash, which, by boiling until the violet color has disap- 
peared, furnishes benzilate of potash, a salt from which 
benzilic acid may be obtained by hydrochloric acid. The 
constitution of Benzilic Acid is Cy.H,,O; + HO. 

Benzone (C,;H,O) is obtained by the distillation of dry 
benzoate of lime at a high temperature, carbonate of lime 
remaining behind. ‘The decomposition is interesting, the 
benzoic acid atom being divided, and yielding benzone 
and carbonic acid. 

CELE ao Oe CO, 

Benzine (C\,H;) arises when crystallized benzoic acid 
-is distilled from hydrate of lime at a red heat. It is an 
oily liquid, and, after being separated from the water which 
comes over with it, isto be rectified. It boils at 187°, so- 
lidifies at 32°, and is lighter than water. In its formation 
the hydrated benzoic acid is resolved into benzine and 
carbonic acid. 

Oe © Pi BRR, ey OFS e REG 81 8S 

Sulphobenzide (C\.H,;SO,) is formed by taking the sub- 
stance which arises from the union of benzine with anhy- 
drous sulphuric acid, and acting upon it with an excess 
of water. The sulphobenzide, which is insoluble in 
that liquid, may be obtained in crystals from its ethereal 
solution. It melts at 212° IF’. From the acid liquid from 
which it has been separated hyposulphobenzic acid may 
be obtained. Its constitution is C\,H,S,O0;,+ HO. 

Mitrobenzide (C,,.H;NO,), produced by the action of 
fuming nitric acid on benzine, with the aid of heat. It is 
an oily liquid, of a sweet taste, heavier than water, and 
boiling at 415°. From it Azobenzide (C\,H;N) may be 
obtained by distillation with an alcoholic solution of caus- 
tic potash, in the form of red crystals. 

Chlorbenzine (C,,H,Cl,) is formed by the union of ben- 
zine and chlorine in the sun-rays. When distilled, the 
solid yields hydrochloric acid and a liquid, Chlorbenzide 
(CH, Cl). 

Eippuric Acid (C,;H;NO;+ HO) is found in the urine 


What is the result of the distillation of dry benzoate of lime? What 
is the nature of the decomposition? "What is the result of the distillation 
of crystallized benzoic acid and hydrate of lime? What is the result of 
the action of anhydrous sulphuric acid and benzine? What is the action 
of nitric acid on benzine ? What substance results from the union of ben- 
zine and chlorine? From what sources may hippuric acid be obtained ? 


THE SALICYLE GROUP. 347 


of graminivorous animals, and occurs in the urine of per- 
sons who have taken benzoic acid. It may be prepared 
by evaporating the fresh urine of the cow, and acidulating 
the concentrated liquor with hydrochloric acid; crystals 
of hippuric acid are deposited, which may be decolorized 
by bleaching liquor and hydrochloric acid. It crystallizes 
in square prisms, sparingly soluble in cold water, of a bit- 
ter taste and acid reaction. Bya high temperature or the 
action of sulphuric acid, it yields benzoic acid. 


THE SALICYLE GROUP. 

There is contained in the bark of the willow and other 
trees a bitter crystalline principle, Saticine (C,;0,,). 
This substance may be extracted by boiling the bitter bark 
in water, and digesting the concentrated solution with ox- 
ide of lead to decolorize it, removing any dissolved lead 
by sulphureted hydrogen, and evaporating until the sali- 
cine crystallizes. It forms white needles of a bitter taste, 
much more soluble in hot than cold water. Distilled with 
bichromate of potash and sulphuric acid, it yields hydro- 
salicylic acid, or the artificial oil of meadow sweet, a sub- 
stance containing Salicyle, the ideal compound radical of a 
series of bodies. 


The Salicyle Group. 


Bantylen CisecOs oo oat a aay 0 ee Set ey 
THivdrosalicyiiG: Gd... a2.) 6 ae ee OL 
lodide of salicyléwpice ap 2805 )o PF SSL. 
OCTET ES a ee ey Sane ee Re — Wal 
&e. &c 


Hydrosalicylic Acid—Oil of Spirea Ulmaria, or Mead- 
ow Sweet (C,,H;0,+H)—is prepared by distilling one 
part of salicine, one of bichromate of potash, two and a 
half of sulphuric acid, and twenty of water; the salicine 
being dissolved in one portion of the water, and the acid 
mixed with the rest. The yellow oil which comes over 
is rectified from chloride of calcium. It may also be ob- 
tained by distillimg the flowers of meadow sweet with 
water. It is transparent, but turns red in the air. It is 
slightly soluble in water, and very soluble in alcohol. Its 
specific gravity is 1:173; it boils at 385° F. It contains 
the same elements as benzoic acid. 

Salicyhie Acid (C\H,O,+ O) is obtained by the action 

Under what circumstances does benzoic acid produce it? From what 


is salicine obtained? What is the constitution of salicyle? How may 
the oil of meadow sweet be made artificially ? 


348 COMPOUNDS OF SALICYLE. 


of hydrate of potash on the foregoing body by the assist- 
ance of heat. After the disengagement of hydrogen is 
over, the mass is dissolved in water, and salicylic acid 
separates in crystals on the addition of hydrochloric acid. 
It is more soluble in hot than cold water, and is charred 
by hot oil of vitriol. 

Chloride of Salicyle (C,,H,O,Cl) is made by the action 
of chlorine on hydrosalicylic acid. Its crystals are insol- 
uble in water, but soluble in solutions of fixed alkalies, 
from which it separates on the addition of an acid, resist- 
ing decomposition even when boiled in caustic potash. 
It unites with caustic potash. 

Bromide and Iodide of Salicyle also exist, but are not 
of interest. 

Chlorosamide (C.H,;N;O;Cl,;).—Ammoniacal gas is ab- 
sorbed by the chloride of salicyle, producing a yellow 
body, which crystallizes from a boiling ethereal solution. 
It is insoluble in water. When acted upon by hot acids, it 
yields a salt of ammonia and chloride of salicyle; an al- 
kali forms with it ammonia and chloride of salicyle. There 
is an analogous bromosamide. 

Salicyluret of Potassium (KS1) is formed by the action 
of oil of meadow sweet on a solution of caustic potash. It 
forms in yellow crystals from its alcoholic solution, and 
has an alkaline reaction. 

Melanie Acid (C\,H,O;) is produced when the crystals 
of salicyluret of potassium are exposed in a moist state to 
the air. They first turn green and then black, and alcohol 
extracts from them melanic acid. 


CINNAMYLE. 
The essential oil of cinnamon is supposed to be the hy- 


druret of an ideal compound radical, cinnamyle, analo- 
_ gous to benzoyle, and yielding a series. 


The Cinnamyle Group. 


Cinndinyld Cis ify Og. 0s 2a genes ee ee a, oe 
Hydruret of cinnamyle Sts of cixtnamon)~. =. . . == C7H. 
Oxide * cinnamic acid) . . . . = C0. 
Chloride 5 Si ot a en ee <= C¢Cl 
&e. &c 


Hydruret of Cinnamyle—Oil of Cinnamon (C,H, O, + 


' What is the constitution of salicylic acid? What is the action of am- 
monia on chloride of salicyle ? Under what circumstances is melanic acid 
produced? What is the essential oil of cinnamon? What is the consti 
tution of cinnamyle ? 


AMMONIA. 349 


H)—is obtained by infusing cinnamon in a solution of 
salt, and then distilling the whole. It is heavier than 
water, and may be separated from that liquid by contact 
with chloride of calcium. 

Cinnamic Acid (C,;H,O, + O) is formed when oil of 
cinnamon is exposed to oxygen gas, the oil becoming a 
white crystalline mass, hydrated cinnamic acid. It may 
also be obtained by boiling hard Tolu balsam with hydrate 
of lime. The cinnamate of lime crystallizes as the solu- 
tion cools, benzoate of lime remaining in solution. The 
crystals are decolorized by animal charcoal, and then de- 
composed by hydrochloric acid; from the hot solution 
cinnamic acid crystallizes. It melts at 248°, and boils at 
560°. It is soluble in boiling water and in alcohol; is 
decomposed by hot nitric acid, and yields benzoic acid, 
with oil of vitriol and bichromate of potash. 

Chlorocinnose (C\;H,Cl,O,) arises from oil of cinna- 
mon by the substitution of four atoms of chlorine for four 
of hydrogen, and is made by the action of chlorine on oil 
of cinnamon by the aid of heat. It crystallizes from its 
alcoholic solution in colorless needles. 


LECTURE LXXVIII. 


Tue Nirrogenizep Princreptes.— AMMONIA and its 
Salts. — CyaNoGEn.— Preparation and Properties of 
Prussic Acid.—Amygdaline and Synaptase—The Cy- 
anides.— Oxygen Acids of Cyanogen. 


Ammontia.—lI have already described, in Lecture LV, 
the compounds of hydrogen and nitrogen, under the 
names of amidogen, ammonia, and ammonium, and have 
also shown the relation there is between the salts of 
potash and soda and those of the oxide of ammonium. 
This compound metal is a hypothetical body; its exist- 
ence may, however, be illustrated by passing a Voltaic 
current through a globule of mercury in contact with 
moist chloride of ammonium, or by putting an amalgam 
of mercury and potassium in a strong solution of that salt. 


How may cinnamic acid be prepared? What is the constitution of 
chlorocinnose, and how is it prepared? What is ammonium ? 
Ge 


350 COMPOUNDS OF AMMONIA. 


The mercury rapidly increases in volume, retaining its 
metallic aspect, becomes of the consistency of butter, with 
a very trivial increase of weight; the resulting substance 
is the Ammoniacal Amalgam. All attempts to insulate 
ammonium from ithave failed. 

The most important salts of ammonia are the following : 

Chloride of Ammonium—Sal Ammoniac—Muriate of Am- 
monia—was formerly brought from Egypt, but is now 
made from the ammoniacal liquors resulting from the 
destructive distillation of animal matters, coal, &c. It is 
soluble in water, crystallizes in cubes or octahedrons, and 
sublimes below a red heat unchanged. It is decomposed 
by lime and potash, and is formed when the vapors 
of ammonia mingle with those of muriatic acid. 

Mtrate of Ammonia is formed by neutralizing nitric 
acid with ammonia. It is deliquescent, and therefore 
very soluble in water. It melts at 240°, and at a higher 
temperature decomposes into steam and protoxide of ni- 
trogen, as is explained in Lecture XLV. 

Carbonates of Ammoma—The neutral carbonate only 
exists in combination. With the carbonate of water it 
unites, forming Bicarbonate of Ammonia, which may be 
prepared by washing the commercial Sesquicarbonate with 
water or alcohol, which leaves it undissolved. The car- 
bonate of ammonia of commerce is prepared by sublima- 
tion from a mixture of sal ammoniac and chalk. Its con- 
stitution is not uniform, though it is commonly regarded 
as a sesquicarbonate. 

Sulphate of Ammonia may be made by neutralizing 
sulphuric acid with carbonate of ammonia. It is soluble 
in twice its weight of cold water, and crystallizes in six- 
sided prisms. 

ydrosulphuret of Ammonia is made by passing sul- 
phureted hydrogen into water of ammonia until no more 
is absorbed. ‘Though colorless at first, it absorbs oxygen, 
and, sulphur being liberated, it turns yellow. It is of 
considerable use as a metallic test. 

Cyanocen.— Bicarburet of Nitrogen (C,N).—The mode 
of preparing this remarkable body, and also its leading 


How is the ammoniacal amalgam prepared? From what sources is sal 
ammoniac derived? For what purpose is nitrate of ammonia employed? 
What is the carbonate of ammonia of commerce? How is hydrosulphuret 
of ammonia made, and what is its use? What is the constitution of cy- 
anogen ? 


HYDROCYANIC ACID. 351 


properties, have been described in Lecture LV. It is ot 
great interest in organic chemistry, as being the first dis- 
tinctly established compound radical, and the best repre- 
sentative of the electro-negative class of those bodies. 

We may call to mind that it is easily made by the de- 
composition of cyanide of mercury at a low red heat, is 
a gaseous body, soluble in water, and, therefore, must be 
collected over mercury. It is combustible, and burns 
with a purple flame. 


The Cyanogen Group. 


VHDORGH CGV) ser at sete | eee 
Hydrocyanic nucidi-\ ©... te SS Ca. 
Sh TS Ti ae a ae eee yy aap O/C 8D 
MUMIATNIG SCIG SP a0 Be ey Malet es) mh a 4, 
Gyanuric ache. 0h 4 fo gene! =a a Os. 
«ce. &e. 


Paracyanogen (C,N).—When the cyanide of mercury is 
decomposed in the process for preparing cyanogen, a 
brownish substance is set free, which is paracyanogen. It 
is insoluble in water and alcohol, and is only remarkable 
in being isomeric with cyanogen. 

Hydrocyanic Acud—Prussic Acid—Cyanide of Hydro- 
gen (C,N + H).—Hydrocyanic acid may be obtained in a 
state of purity by passing dry sulphureted hydrogen gas 
over dry cyanide of mercury in a tube, and conducting 
the vapor, which is evolved when the tube is warmed, into 
a vial immersed in a freezing mixture. The result of the 
decomposition is sulphuret of mercury and hydrocyanic 
acid. In a state of aqueous solution, it is best obtained by 
the action of dilute sulphuric acid on the ferrocyanide of 
potassium in a retort, and receiving the vapor ina Liebig’s 
condenser. Having ascertained the strength of the prod- 
uct, it may.then be diluted to the proper point. This ex- 
amination may be conducted by precipitating a known 
weight of the acid with nitrate of silver in excess, collect- 
ing the cyanide of silver on a weighed filter, washing, 
drying, and reweighing, which gives the weight of the 
cyanide. This, divided by five, is the weight of the pure 
hydrocyanic acid, nearly. 

Anhydrous hydrocyanic acid is a colorless and very vol- 
atile liquid, which exhales a strong odor of peach blooms ; 


What interesting fact is connected with its discovery? What are its 
properties? What is paracyanogen? How may hydrocyanic acid be 
mode? By what process can its strength be determined? 


302 2 AMYGDALINE,. 


has a density of *705; boils at 79°. It mixes with water 
and alcohol in any proportion. A drop of it held in the 
air on a glass rod becomes solidified by the rapid evapora- 
tion from its surface. In the sunlight it decomposes rap- 
idly, producing a dark-colored substance ; and the same 
change goes on, though much more slowly, in the dark. 
It is one of the most insidious and terrible poisons, a few 
drops producing death in a few seconds; and even its 
vapor, largely diluted with air, brings on very unpleasant 
symptoms. Under the action of strong acids it is decom- 
posed into ammonia and formic acid, the change being 
very simple : 
CLN, H + 3HO = NH, + C,HO,. 

Under such circumstances, hydrochloric acid yields mu 
riate of ammonia and hydrated formic acid. Hydrocy 
anic acid may, to a certain extent, be preserved from 
spontaneous change by the presence of a minute quantity 
of any mineral acid. 

Prussic acid may be detected by its smell, and by yield- 
ing a precipitate of Prussian blue when acted upon in so- 
lution successively by sulphate of iron, potash, and an ex- 
cess of hydrochloric acid. The liquid in which the poison 
is suspected to exist should be acidulated with sulphuric 
acid and distilled, and the hydrocyanic acid will be found 
in the first portions which come over. 

Amygdaline ( Cy Hy,NO..).—A crystallizable substance 
found in bitter almonds, the kernels of peaches, &c.; is of 
considerable interest in connection with hydrocyanic acid, 
inasmuch as these organic bodies yield, when distilled witk 
water, that substance. The change consists in the ac- 
tion of water upon amygdaline by the aid of an azotized 
ferment called Synaptase, or Emulsine, which constitutes 
the larger portion of the pulp of almonds; the bitter al- 
mond oil at the same time makes its appearance. Amyg- 
daline may be abstracted from the paste of bitter almonds, 
from which the fixed oil has been expressed, by the aid 
of boiling alcohol, which being subsequently distilled off, 
the sugar which is contained in the sirupy residue is de- 
stroyed by fermentation with yeast. The liquid being 


What are its properties? What is the action of strong acids upon it? 
How may it be partially preserved from spontaneous change? How may 
. it be detected? What is amygdaline? What is the ectien of synaptase 
and water upon it? How may it be obtained? 


COMPOUNDS OF CYANOGEN. 353 


evaporated again to a sirup, is mixed with alcohol, which 
precipitates the amygdaline as a white crystalline pow- 
der, purified by being redissolved in alcohol and left to 
cool. It is soluble in hot and cold water, but sparingly 
soluble in cold alcohol. .A weak solution of it in water, 
under the influence of a small quantity of the emulsion of 
sweet almonds, yields at once oil of bitter almonds and 
hydrocyanic acid. When amygdaline is boiled with an 
alkali, it yields Amygdalinic Acid, which forms a salt with 
the alkali, and ammonia is evolved. 

Cyanide of Potassium (KCy) may be formed by the di- 
rect union of cyanogen and potassium, or by the ignition 
of the ferrocyanide of potassium in a close vessel. For 
common purposes in the arts it may be formed in a state 
somewhat impure by mixing eight parts of ferrocyanide 
of potassium, rendered anhydrous by heat, with three of 
carbonate of potash, also dry, and fusing the mixture in a 
crucible, stirring it until the fluid part of the mass is col- 
orless. The sediment is allowed to settle, and the clear 
liquid poured off; it is the substance inquestion. Cyanide 
of potassium is very soluble in water, yields colorless oc- 
tahedral crystals, which deliquesce in the air; it melts 
without change at a red heat, and exhales the odor of 
prussic acid. It is very poisonous. 

Cyanide of Mercury may be made by dissolving red 
oxide of mercury in hydrocyanic acid, or by the action of 
a solution of ferrocyanide of potassium on sulphate of 
mercury; the cyanide crystallizing from the filtered hot 
solution. It forms fine prismatic crystals, more soluble in 
hot than cold water. It is poisonous; and, when decom- 
posed at a low red heat, yields cyanogen gas. 

Cyanic Acid (CyO+ HO) is procured by heating ina re- 
tort cyanuric acid, deprived of its water of crystallization; 
a colorless liquid comes over into the receiver, which is 
the hydrated cyanic acid; it has a strong odor like acetic 
acid, and produces blisters on the skin. It is decomposed 
by the contact with water into bicarbonate of ammonia. 


C,NO, HO+ 2HO...=...C,0,+ INA;, 


and is a very instable body, spontaneously changing in a 
short time into Cyamelide, a body of the same constitu- 


By what processes may the cyanide of potassium be made? How ma 
the cyanide of mercury be prepared? Exposed to heat, what does it 
yield? What are the ere ce and properties of cyanic acid ? 

G2 


354 DERIVATIVES OF CYANOGEN. 


tion, but a white opaque solid, insoluble in water and al- 
cohol, and decomposed by hot oil of vitriol into carbonate 
of ammonia. 

Fulminic Acid (Cy,0,+2HO) has not yet been insula- 
ted, but some of its salts, presently to’ be described, are 
characterized by the violence with which they detonate 
under very trivial disturbances. It is a bibasic acid. 

Cyanuric Acid (Cy;03+3HO) may be made by heating 
urea, which disengages ammonia; the residue is dissolved 
in hot sulphuric acid, and nitric acid added until the 
liquid becomes colorless: on mixing it with water, and 
allowing it to cool, the cyanuric acid separates. Its crys- 
tals are efflorescent; it is sparingly soluble in water, and is 
a tribasic acid; and, as has been already stated, at a red 
heat it may be distilled, and yields cyanic acid without 
any other product. 


LECTURE LXXIX. 


Bopies ALLIED To CyanocEen.—Salis of the Oxycyano- 
gen Acids.—F nrrocyanoGcEen.— Ferrocyanides of Hy- 
drogen and Potassium— Prussian Blue and Basic Blue. 
— FERRIDCYANOGEN.—SULPHOCYANOGEN.— Compounds 
with Hydrogen and Potassium.— Melam, Melamine, &c. 


Cyanate of Potash (KO, CyO) may be prepared by ox- 
ydizing cyanide of potassium by oxide of lead in an earth- 
en crucible; the result boiled with alcohol yields, on cool- 
ing, crystals of cyanate of potash, in thin, transparent 
plates, which undergo no change in dry air, but with 
moisture become converted into bicarbonate of potash 
and ammonia. 

Cyanate of Ammonia— Urea (C,H,N,O,).—The vapor 
of hydrated cyanic acid, mixed with ammoniacal gas, 
yields cyanate of ammonia. ‘The solution in water, when 
heated, gives off ammonia, and the cyanate changes into 
Urea, from which caustic alkalies can not disengage am- 
monia. Urea may also be made from the action of sul- 
phate of ammonia or cyanate of potash. 


~ ‘What of fulminic acid? What of cyanuric acid? How is the cyanate 
of potash made? How may urea be formed artificially ? 


SALTS OF FULMINIC ACID. 355 


Fulminate of Silver (2Ag0O, C,N,O,) is made by dis- 
solving silver in warm nitric acid and adding alcohol. It 
separates from the hot liquid in white grains, which, being 
washed in water, are dried in small portions on filtering 
paper. It detonates with wonderful violence when ei- 
ther struck or rubbed. It is sparingly soluble in hot wa- 
ter, and crystallizes from that solution on cooling. It 
yields, by digestion with water and metals, salts, as those 
of zinc and copper. 

Fulminate of Mercury (2HgO, C,N,O,) is prepared in 
the same manner as the foregoing, and, like it, is very ex- 
plosive. It is used for making percussion caps. 

Chloride of Cyanogen (Cy Cl) is prepared by the action 
of chlorine on moist cyanide of-mercury in the dark. It 
is a colorless gas, soluble in water, congeals at 0°, and 
boils at 11°; condenses into a liquid under the pressure 
of four atmospheres. When kept in this condition, in 
sealed tubes, for a length of time, it assumes the solid 
state, which form may also be given to it by acting on an- 
hydrous hydrocyanic acid by chlorine in the sun’s rays; 
hydrochloric acid is formed, and the solid cyanide crys- 
tallizes. It exhales a peculiar odor, melts at 284°, and 
is soluble in alcohol and ether. : 


FERROCYANOGEN. 

Ferrocyanogen (C,N;Fe = Cfy) is an ideal compound 
radical. 

HTydroferrocyanic Acid (Cfy, 2H) may be obtained by 
decomposing the insoluble ferrocyanide of lead by sul- 
phureted hydrogen while suspended in water. The so- 
lution being filtered, is to be evaporated with sulphuric 
-acid in vacuo until the acid is left solid. It may also be 
prepared by agitating its aqueous solution with ether, or 
by adding hydrochloric acid to a strong solution of ferro- 
cyanide of potassium, and then mixing it with ether, which 
precipitates the acid. It is soluble in water, to which it 
gives a powerful acid reaction. It decomposes alkaline 
carbonates with effervescence, and does not dissolve ox- 
ide of mercury in the cold. In these respects, therefore, 
it strikingly differs from hydrocyanic acid. 


What is the process for preparing fulminating silver, and what are its 
properties? For what purpose is fulminate of mercury used? What re- 
sults from the action of chlorine on cyanide of mercury in the dark? What 
is ferrocyanogen? How is hydroferrocyanic acid obtained ? 


356 COMPOUNDS OF FERROCYANOGEN. 


Ferrocyanide of Potassium — Prussiate of Potash — 
(2.K, Cfy+ 3HO).—This salt is made on the large scale by 
igniting potash, iron filings, and animal matters in an iron 
vessel; the mass is then acted upon by hot water, which dis- 
solves out a large quantity of cyanide of potassium, which 
is converted into the ferrocyanide by the iron, and the 
filtered solution, on cooling, yields it in lemon-colored 
crystals, soluble in four parts of cold water. It is not 
poisonous. At a red heat it decomposes, and yields cy- 
anide of potassium. It is a very valuable reagent ; with 
copper it yields a chocolate precipitate ; with protoxide 
of iron, a white ; and with peroxide of iron, Prussian blue. 

Common Prussian Blue (3 Cfy + 4 Fe) is prepared by 
precipitating a persalt of iron by solution of ferrocyanide of 
potassium; when dry, it is of a deep blue, with a lustre of 
coppery-red. It is msoluble in water, is decomposed by 
alkaline solutions, which yield alkaline ferrocyanides, and 
precipitate oxide of iron. It is soluble in solution of ox- 
alic acid, and then constitutes the basis of blue writing 
inks, which are used for steel pens. It is also much em- 
ployed as a paint. 

Basic Prussian Blue (3 Cfy,4Fe + FeO;) is formed when 
the white precipitate, yielded by a protosalt of iron with 
ferrocyanide of potassium, is exposed to the air. As its 
formula shows, it is common Prussian blue, with perox- 
ide of iron. It differs from Prussian blue in the remark- 
able peculiarity that it is soluble in pure water. 


FERRIDCYANOGEN. 
. Ferridcyanogen (C,N;,Fe, = Cfdy)—A hypothetical 
compound radical, which yields some compounds of in- 
terest. 

Ferridcyanide of Potassium (3K + Cfdy) may be made 
by passing chlorine through a dilute solution of ferrocy- 
anide of potassium until it ceases to yield a precipitate 
with a persalt of iron. The liquid being concentrated, 
yields, on cooling, deep-red crystals, the solution of which 
is of a greenish color. It gives no precipitate with perox- 
ide of iron, but with the protosalts a bright blue, lighter 
than Prussian blue, and known as Turnbull’s Blue. 


How is the prussiate of potash prepared? Isit poisonous? Whatcolor 
does it give with protoxide and peroxide of iron? What is common 
Prussian blue? "What is its composition? For what purposes is it used? 
In what respect does basic Prussian blue differ from it? What is the con- 
stitution of ferridcyanogen? Whatis Turnbull’s blue? 


— 


SULPHOCYANOGEN. 357 


Cobaliocyanogen, a hypothetical radical, yielding com- 
pounds analogous to the preceding bodies. 

Sulphocyanogen (C,NS,) (Csy), a compound radical, not 
yet insulated with certainty. Its formula shows that it is 
a bisulphuret of cyanogen. 

Hydrosulphocyanic Acid (CsyH) may be obtained by 
decomposing sulphocyanide of lead by sulphureted hy- 
drogen in water. The solution is decomposed by ebulli- 
tion. It has the odor of acetic acid. It yields with per- 
oxide of iron a blood-red color. 

Sulphocyanide of Potassium (KCsy) may be made by 
heating powdered ferrocyanide Me potassium with half its 
weight of sulphur and one third of carbonate of potash, 
and keeping it melted for a short time. The mass is then 
boiled with water, which dissolves out the sulphocyanide, 
and the solution being concentrated, yields prismatic crys- 
tals of the salt. It is soluble in water and alcohol, and 
deliquesces in the air. It melts at a red heat. Its solu- 
tion with peroxide of iron yields a blood-red color. 

Melam (C,,H,N,;) is produced when sulphocyanide of 
ammonium is distilled at a high temperature, or by heating 
dry sulphocyanide of potassium with twice its weight of 
sal ammoniac. It is insoluble in water, but dissolves in 
strong sulphuric acid. When heated, it yields mellone 
and ammonia. 

Melamine ( C;H,.N,) is produced when melam is dissolv- 
ed in a hot solution of potash. It separates on cooling. 
It is a basic body, uniting with acids. 

Ammeline (C;H;N;O,) remains in the solution after the 
melamine has crystallized. It may be precipitated with 
acetic acid. 

Ammelide (C,,.H,N,O;5) is prepared by dissolving amme- 
line in sulphuric acid, and precipitating with alcohol. 


What are cobaltocyanogen and sulphocyanogen? ‘What color does 
hydrosulphocyanic acid yield with peroxide of iron? By what process is 
sulphocyanide of potassium made? What results from the distillation of 
the sulphocyanide of ammonium? What are melamine, ammeline, and 
ammelide ? 

R 


358 MELLONE. 


LECTURE LXXX. 


Me._tone—Urea.— Mellone, Preparation of.—Mellonides 
of Hydrogen and Potassium—WNatural and artificial 
Formation of Urea—Uric Acid.—Its Properties.—De- 
rivatives of Uric Acid —Parabanic, Oxaluric, and Thi- 
onuric Acids.—Alloxantine.—Purpurate of Ammonia.— 
Xanthic and Cystic Oxides. 


Me.uone (C,N, =Me).—If sulphocyanide of potassium 
be acted upon by chlorine or nitric acid, a yellow pow- 
der is deposited; this, when heated, gives off bisulphuret 
of carbon and sulphur, and there is left a yellowish pow- 
der, which is mellone. ‘The relation of its constitution 
with cyanogen is obvious. It resists a moderate heat with- 
out change. 

Hydromellonic Acid (MeH)—By adding hydrochloric 
acid to a hot solution of mellonide of potassium, this acid 
separates as a white powder on cooling. Té is partially 
soluble in hot water, and possesses strong acid powers. 

Mellonide of’ Potassium (K Me) may be prepared by melt- 
ing ferrocyanide of potassium with half its weight of sul- 
phur, and adding, when the fusion is complete, five per 
cent. of dry carbonate of potash. The resulting mass is 
acted on by water, and the solution being filtered, is evap- 
orated, until, on cooling, it forms a mass of crystals, from 
which the sulphocyanide may be removed by alcohol, and 
the mellonide left. It is soluble in water, and yields, by 
double decomposition with the salts of baryta, lime, &c., 
mellonides of these bodies, for the most part sparingly 
soluble. 

Urea (C,H,N,O,) may be obtained from urine by add- 
ing to it, when concentrated, a strong solution of oxalic 
acid. ‘The precipitated oxalate of urea is to be boiled 
with powdered chalk, and the filtered solution concentra- 
ted until the urea crystallizes on cooling. It may also be 
made artificially by adding to a strong solution of cyanate 
of potash an equal weight of dry sulphate of ammonia ; 
the solution is evaporated to dryness in a water bath, and 


How is mellone prepared? What is the action of hydrochloric acid on 
the mellonide of potassium? How may urea be made artificially ? 


URIC ACID. 359 


the urea dissolved out by alcohol. It crystallizes in prisms, 
very soluble in water, but permanent in the air. Ata 
high temperature it gives off ammonia and cyanate of 
ammonia, cyanuric acid remaining. Urea contains the ele- 
ments of cyanate of oxide of ammonium, has neither an 
acid nor alkaline reaction, is decomposed by hot alkaline 
solutions, with evolution of ammonia, and, by uniting with 
two atoms of water, yields carbonate of ammonia, a result 
which takes place during the putrefaction of urine, the 
change being brought on by a nitrogenized ferment — 
the mucus of the bladder. Urea unites with acids, and 
forms, with nitric and oxalic acids, characteristic salts. 

Uric Aced—Luthic Acid ( C,,H,N,O,)—may be obtained 
from the solid urine of serpents, which, being boiled in 
solution of caustic potash and filtered, yields uric acid, by 
the addition of hydrochloric acid, as a white, inodorous, and 
sparingly soluble powder; soluble without change in sul- 
phuric acid, from which it is precipitated by water. Uric 
acid also exists in human urine, and appears to be always 
a product of the action of the animal economy. Of its salts, 
the urate of soda is interesting; it is the chief ingredient 
of gouty concretions in the joints, called chalk-stones. 
The urate of ammonia occurs as a urinary calculus, and 
is often deposited from urine as a reddish cloud or pow- 
der. 

Allantoin (C,H;N,O;) is prepared by boiling uric acid 
with peroxide of lead; the filtered solution, being con- 
centrated, deposits prismatic crystals of allantoin on cool- 
ing. It is soluble in 160 parts of cold water. By a solu- 
tion of caustic alkali it is decomposed into ammonia and 
oxalic acid, assuming, during this change, the elements 
_of three atoms of water. 

Alloxan (C,H,N,O,.) is made by the action of concen- 
trated nitric acid on uric acid in the cold. The uric acid 
is to be added in small portions successively, until about 
one third the weight of the nitric acid has been used. An 
effervescence takes place, and there is left a white mass, 
from which the excess of acid is to be drained. The sub- 
stance is then to be dissolved in hot water and crystallized. 


What are its properties? To what substance does it give rise in fer- 
mentation? Under what circumstances does uric acid occur? What are 
vshalk-stones? Under what form does urate of ammonia occur? How 
may alanine be prepared? What is the action of cold nitric acid on uric 
acid 7 


360 ALLOXANIC ACID. 


Its solution has an acid reaction and a bitter taste, and 
stains the skin purple, and, with a protosalt of iron and an 
alkali, yields a characteristic blue compound. 

Alloxanic Acid (CHINO, + HO) may be prepared by 
decomposing the alloxanate of baryta by dilute sulphuric 
acid. The alloxanate itself is obtained by the addition 
of barytic water to a warm solution of alloxan. It is a 
strong acid, decomposing carbonates, and even water, by 
the aid of zinc. | 

Mesoxalic Acid (C,O, + 2HO).—Mesoxalic acid may 
be obtained by boiling a solution of alloxan with acetate 
of lead, the resulting mesoxalate of lead being decom- 
posed by sulphureted hydrogen. It is a strong acid, re- 
sists a boiling heat, and is bibasic. 

Mykomelinic Acid (C,H;N,O;) is prepared by boiling a 
solution of alloxan with an excess of ammonia, and then 
precipitating by an excess of dilute sulphuric acid. It is 
a light yellow powder. 

Parabanic Acid (C,N,O, + 2HO) is formed by the ac- 
tion of strong nitric acid on alloxan, or uric acid, by the 
aid of heat. The crystals form on cooling, and may be 
dried by draining, and then recrystallized. It is soluble 
in water, reddens litmus, and forms beautiful prismatic 
crystals. 

Oxaluric Acid (C;H;N,O, + HO) may be made by de- 
composing a hot solution of the oxalurate of ammonia by 
dilute sulphuric acid, and cooling rapidly. The ammonia 
salt is itself procured by boiling a solution of the para- 
banate of ammonia, when it crystallizes, on cooling, in 
small needles. Oxaluric acid is a white crystalline pow- 
der ; it contains the elements of one atom of parabanic 
acid and three of water, and its solution, by boiling, yields 
oxalic acid and oxalate of urea. 

Thionuric Acid (C,H,N;S,0,. + 2HO), a bibasic acid 
prepared by decomposing thionurate of lead with sul- 
phureted hydrogen. It contains the elements of one atom 
of alloxan, one of ammonia, and two of sulphurous acid. 

Uramile (C;H;.N;O,;)—When an excess of a saturated 
solution of sulphurous acid in water is mixed with a cold 


How is alloxanic acid prepared? What substance results from boiling 
alloxan with acetate of lead? How is mykomelinic acid prepared? 
What substance results from the action of hot nitric acid on uric acid ? 
What is the relation between oxaluric and parabanic acid? How is 
uramile prepared ? 


ALLOXANTINE.—MUREXIDE. 361 


solution of alloxan, and an excess of carbonate of ammo- 
nia with caustic ammonia added, and the whole boiled, 
the thionurate of ammonia is deposited on cooling. From 
this the lead salt, used in the preparation of the foregoing 
acid, may be obtained by acetate of lead. The thionurate 
of ammonia, with a little hydrochloric acid, being boiled 
in a flask, there separates a white body, which is uramile. 
It differs from thionuric acid in not containing the ele- 
ments of two atoms of sulphuric acid. If the thionurate 
of ammonia is mixed with dilute sulphuric acid and evap- 
or ated in a water bath, Uramilic Acid is deposited ; it is 

Jc LL,oN; Or; 

Wiitcer,e (C,H;N,O,) is made when sulphureted 
hydrogen gas is passed through a cold solution of alloxan. 
The product is filtered, washed, and boiled in water, 
which deposits the alloxantine, on cooling, in transparent 
rhombic prisms, which turn red on exposure to ammonia. 
This substance is alloxan, with one atom of hydrogen. A 
hot solution of it is decomposed when a stream of sulphur- 
eted hydrogen is passed through it, and Dialuric Acid 
forms. 

Murexide—Purpurate of Ammonia (C,,H,N,O.)—may 
be made by the action of dilute nitric acid on uric acid, 
and then adding ammonia, or by boiling equal weights of 
uramile and red oxide of mercury with eighty times their 
weight of water, rendered alkaline by ammonia. The 
liquid turns of a deep purple color, and, when filtered, 
deposits, on cooling, crystals of murexide in square 
prisms, which, by reflected light, are of a green metallic 
lustre, and, by transmitted light, ‘of a purple. It is spar- 
ingly soluble in cold water, but much more so in hot, and 
is one of the most splendid compounds known. 

Murexan—Purpuric Acid—Murexide is to be dissolved 
in a solution of caustic potash, and dilute sulphuric acid 
added. It forms a yellow powder, and, dissolved in am- 
monia, gives rise to the foregoing body. 

Xanthic Oxide (CEH, N,O,) occurs as a urinary calculus 
of a brown color and waxy aspect. The calculus may 
be dissolved in dilute potash, and xanthic oxide precipi- 


How is alloxantine prepared? What is the action of dilute nitric acid 
and ammonia on uric acid? What is the color of the crystals of murexide ? 
How may murexan be prepared? Under what circumstances do xanthie 
oxide and cystic oxide occur ? 

lin 


362 THE VEGETABLE ACIDS. 


tates as a white powder by carbonic acid. It is a waxy 
body. 

Cystic Oxide (C,;H;NS,O,) occurs also as a urinary 
calculus. 


LECTURE LXXXI. 


Tue VecetTasLe Acips.—Tartaric Acid, Preparation 
of —Salts of Tartaric Acid— Acids allied to Tartar- 
tc.—Citric and its allied Acids.—Malic and its allied 
Acids. ——Tannic Acid.—Gallic Acid.— Acids allied to 
them. 


Or the vegetable acids several will be described with 
their associated alkalies. The following are those of 
which I shall treat in this Lecture: 


Tartare. 2.6 o> bin’ #0aiO@ + 2he 
Paratartaric . ... .. - Cs H:Oi.+ 2H0O. 
Pyrotartarie ©. 83%, 0 2ST So Ce FEO} + FTO 
Tarivahic, > .2. “on ow) RPGs Ow -- SHO 
Wartveuc ia 0s 0 ie ee Oy fF HO. 
Cie ooo es = mdi et Sele. 
Acegine,; .) Fe oc Perce Mee es HO. 
Malee~ Ses). ¢ acu se Geet. 1-90 Gee 2HO. 
PO pak i ee ee oe we 8 2HO. 
Famane ? Py Oe OC -Cee es Os HO. 
Tanai. aoe 44 ee et EEO -- 38a 
alle eee. eas ea ns) tie he ee Dk ele BETS 
SS Pen gh a os we ns nye eee eee. 
Poroealent F208 Se ae 
Motazallic , leis Wey, : C6 H2 Ox. 


Besides acids such as these, which constitute a very nu- 
merous group, there is another class, which pass under 
the name of Coupled Acids, the peculiarity of which is, that 
they consist of an acid affixed or coupled to another body, 
which, without affecting the neutralizing power of the 
acid, accompanies it in allits combinations. Thus, hypo- 
sulphuric acid couples with naphthaline to form hyposul- 
phonaphthalic acid, which neutralizes just as much of any 


base as hyposulphuric acid itself could do, the naphtha- . 


line not changing its powers. 

Tartaric Acid (C,H,O,.+2HO).—A bibasic acid which 
occurs, as has been already stated, in the juice of grapes 
and other fruits as bitartrate of potash. It may be ob- 
tained by dissolving cream of tartar in boiling water and 


What are coupled acids? From what source is tartaric acid derived ? 


; 
; 


ew ey 


SALTS OF TARTARIC ACID. 363 


adding powdered chalk, a tartrate of lime precipitating. 
The rest of the tartaric acid may be obtained from the so- 
lution by the addition of chloride of calcium, which yields 
another portion of tartrate of lime, which may be decom- 
posed by digesting with an equivalent proportion of dilute 
sulphuric acid. The concentrated and filtered solution 
yields crystals acid to the taste, inodorous, and soluble 
both in water and alcohol; the solution decomposes by 
keeping. Tartaric acid yields several valuable salts. 

Tartrate of Potash—Soluble Tartar (2KO, CzH,O,.)— 
may be made by adding carbonate of potash to cream of 
tartar. It is very soluble. 

Bitartrate of Potash—Cream of Tartar (KO, HO, 
C,H,O,,)—This is the salt which is deposited from the 
juice of the grape during fermentation, as Argo/. It may 
be purified from the coloring matter it contains by solution 
in hot water, and the action of animal charcoal. In cold 
water it is very sparingly soluble. It yields black flux 
when ignited in a close vessel, the black flux being car- 
bonate of potash enveloped in carbonaceous matter. 

Tartrate of Potash and Soda—Rochelle Salt—Salt of 
Seignette (ILO, Na O, C,H,O,.+10HO)—may be procured 
by neutralizing a solution of the foregoing salt with car- 
bonate of soda. On evaporation and cooling it separates 
in large, prismatic crystals. 

- Tartrate of Antimony and Potash — Tartar Emetic 
(KOS6,0;, C,H,O,+2HO)—This valuable medicinal 
agent is made by boiling oxide of antimony with a solu- 
tion of cream of tartar; on cooling, the crystals are depos- 
ited. They are much more soluble in hot than in cold 
water, and dissolve without decomposition. 

Racemic Acid—Paratartaric Acid.—This remarkable 
acid, which has the same constitution as tartaric acid, and 
resembles it very closely, is found in the grapes of certain 
parts of Germany and France. Racemic acid, however, 
differs from tartaric in yielding a precipitate with a neu- 
tral salt of lime. 

Pyrotartaric Acid (C;H,O;+HO) is obtained by the 
destructive distillation of tartaric acid, coming over with 
a variety of other products. 


W hat is soluble tartar? From what source is cream of tartar derived ? 
What is Rochelle salt? How is tartar emetic prepared? What is the 
relation between racemic and tartaric acids? 


364 CITRIC ACID. 


The action of heat on tartaric acid is remarkable. When 
exposed to a temperature of 400° I’., it melts, throws off 
water, and yields in succession three different acids, tar- 
tralic, tartrelic, and anhydrous tartaric acid, the constitu- 
tion of which, compared with tartaric acid, is as follows; 


Tartaric acid G45 CO - eno. 
Tartralic “6s fix.) >. x, oy « ee CgH sna 20. 
Tartrouy, io a sn ts gs ee ae A peda aig ts Pak 
Anhydrous tarfaric 4 “32” .°'.°C'"=, A, On. 


All these, by the continued contact of water, pass back 
into the condition of tartaric acid. 

Citric Acid (C,,H;O,,+3HO), a tribasic acid, occurring 
abundantly in the juice of lemons and other sour fruits, 
and separated therefrom by the aid of chalk and sulphur- 
ic acid. It is clarified by digestion with animal charcoal, 
and yields prismatic crystals of a pleasant taste, and sol- 
uble both in hot and cold water. The crystals are of two 
different forms, according to the conditions of their forma- 
tion; those which separate in the cold by spontaneous 
evaporation contain five atoms of water, three of which 
are basic; but those which are deposited from a hot solu- 
tion contain only four. 

The citrates form a very numerous family of salts, for, 
as the acid is tribasic, we may have them with three atoms 
of metallic oxide, or two of oxide and one of water, or one 
of oxide and two of water, besides subsalts. 

Aconitic Acid— EL quisetic Acid (CHO; + HO)—is form- 
ed by fusing citric acid, and the resulting brown product 
is dissolved in water, the change being 

Ct Oye op stg) tO ELL Ne 
that is, one atom of hydrated citric acid yields three of 
aconitic acid and five of water. Aconitic acid is remark- 
able from occurring naturally in the Aconitum Napellus and 
Equsetum Fluviatile. 

Malic Acid (C,;H,O,-+ 2HO), a bibasic acid, occur- 
ring in the juice of apples and other fruits. It may also 
be prepared from the stalks of rhubarb, in which it occurs 
with oxalate of potash. It is a colorless solid, soluble in 
water, the solution changing by keeping. When heated 
in a retort, it melts, and then boils, emitting a volatile 


Describe the action of heat on tartaric acid. From what source is citric 
acid obtained? How many classes of salts does citric acid yield? What 
substance results from the fusion of citric acid? From what sources is 
malic acid derived ? 


TANNIC ACID. 865 


acid, the Maleic Acid, C,H,O, + 2HO, which condenses 
with the water in the receiver; at the same time there 
forms in the retort crystalline scales of Fumarie Acid, 
C,HO, + HO, which may be separated from the unchang- 
ed malic acid by solution in cold water. It is to be ob- 
served that maleic, fumaric, and aconitic acids are isomer- 
ic bodies. 

Tannic Acid (C\.H,O, + 3HO).—An astringent princi- 
ple found in the bark of the oak, nut-galls,and Fig. 272. 
other vegetable productions. It may be sep- ce 
arated by placing in a vessel, 6, Fig. 272, 
powdered galls. On pouring on them sulphu- 
ric ether, a liquid drops through the funnel 
tube, c, into the bottle, a, spontaneously sepa- 
rating into two portions; the lower, which is 
a solution of tannic acid in water, is to be de- 
canted and evaporated in presence of sul- 
phurig acid in vacuo. It yields tannic acid, 
or tannin, in the form of an uncrystallized 
mass. ‘Thisacid is soluble in water, but much 
less so in ether, has an astringent taste, and 
reddens litmus paper. With the persalts of 
iron it yields a characteristic and valuable precipitate of 
a black color, the basis of common writing ink. It forms 
insoluble compounds with starch, gelatine, and other or- 
ganic bodies, that with gelatine being of considerable in- 
terest. It is the basis of Jeather. From the characteris- 
tic precipitate it gives with that metal, it is used as a test 
for iron, which must, however, be in the state of peroxide, 
as the protosalts are unacted upon. The gradual dark- 
ening of pale writing inks is due to the gradual oxydation 
- of the iron they contain. 

Catechin (C,;H;0;)—There is a body extracted by hot 
water from catechu, calied catechin. It crystallizes in 
needles, and does not form an insoluble compound with 
gelatine, and gives a green color with persalts of iron. By 
the action of caustic potash in excess, it yields a black and 
insoluble substance, Japonic Acid. By the action of car- 
bonate of potash, it yields Rudinic Acid. 


What two acids are yielded by it under the action of heat? What is 
the relation between maleic, fumaric, and aconitic acids? How is tan- 
nic acid made? What color does it yield with persalts of iron? What is 
the basis of leather? From what cause do pale writing inks darken ? 
What is catechin? 

tn 2 


366 GALLIC ACID. 


Gallic Acid (C,HO, + 2HO) may be formed by expos- 
ing a solution of tannic acid to the air, or by making 
powdered galls into a paste with water, and keeping it 
exposed in a warm place to the air for some weeks. ‘The 
mass is then pressed and boiled with water. On cooling, 
the solution precipitates a quantity of gallic acid, which 
may be purified by re-crystallization. Like tannic acid, 
this substance yields no precipitate with a protosalt of 
iron, but a deep blue-black with a persalt. It does not, 
however, precipitate gelatine. Its crystals are soluble in 
one hundred parts of cold and three parts of boiling wa- 
ter. The solution has an astringent taste. 

Tannic acid passes into gallic acid by oxydation, carbon- 
ic acid and water being evolved. 


C,H,0,, + Os... =... 2(C, HO; + 2H0) + 2(H0) 
+ 4(CO,); 
that is, one atom of tannic acid and eight of oxygen yield 
two of gallic acid, two of water, and four of carbonic acid. 

Ellagic Acid (C,H,O,), or gallic acid minus one atom 
of water, may be extracted after the removal of gallic acid 
by analkali, and precipitated as a gray powder by hydro- 
chloric acid. 

Pyrogallic Acid (C,;H;O;) sublimes when gallic acid is 
heated in a retort to 420°. It is inthe form of white crys- 
tals, which are soluble in water. It strikes a black color 
with the protosalts of iron. 

Metagallic Acid (C,H,O,) is formed when gallic acid is 
suddenly heated in a retort to 500°. It is a black mass, 
insoluble in water, but soluble in alkalies, from which it 
is precipitated as a black powder by acids. 


How may gallic acid be prepared? How is ellagic acid procured? 
What is the action of heat on allic acid? 


VEGETABLE ALKALIES. 367 


LECTURE LXXXII. 


THe VEGETABLE ALKALIES.—General Properties of Veg- 
etable Alkalies— Morphia.—Its Preparation and Prop- 
erties — Other Alkalies of Opium.— Meconic Acid.— 
Alkalies of Bark, Quina, Cinchona, §&¢c.—Kinic Acid.— 
Strychnia and Brucia— Table of Alkaloids.— Artificial 
Alkaloids. . 


Tue vegetable alkalies constitute an extensive class of 
bodies, which are, for the most part, the active medicinal 
agents of the plants in which they occur. They are gen- 
erally sparingly soluble in water, but more soluble in 
boiling alcohol, of a bitter taste, and characterized by 
containing nitrogen. In their natural state they are unit- 
ed with an acid, and, possessing basic properties in a very 
marked manner, neutralize acids completely. This qual- 
ity seems to depend on the nitrogen they contain, and 
has no reference to their oxygen, for the quantity of this 
latter element which may be present seems to have no 
relation to their neutralizing power, and, indeed, in some 
of them it is not present at all. In many respects. they 
are analogous to ammonia, their salts, unlike those of 
some of the compound radicals, such as ethyle, &c., un- 
dergoing decomposition in the same manner as the salts 
of ammonia. ‘Thus, the chloride of ethyle does not de- 
compose the nitrate of silver, but the analogous com- 
pounds of ammonia and the vegetable alkalies do; and 
these bodies may, therefore, be separated from the natural 
combinations in which they occur precisely as we should 
separate lime, or potash, or magnesia in their salts. 
Most of the vegetable alkalies are poisonous bodies, and, 
indeed, among them we meet with some of the most ter- 
rific poisons known. ‘There are several recently-discov- 
ered artificial substances, such as Anzline, and those con- 
taining arsenic and platinum, which ought to be classed 
with these basic bodies. 


What are the vegetable alkalies? What element do they all contain? 
In what condition are they commonly found? What are their relations to 
acid bodies? What are their general properties? Have any of them 
been made artificially ? 


368 MORPHIA.—NARCOTINE. 


Of the numerous vegetable alkalies, those which I shall 
now describe are the most important. 

Morphia (C,,INO, + 2HO).—This substance is the 
active principle of opium, and was the first discovered of 
these alkalies. It was insulated by Sertuerner in 1803. 
It may be prepared by mixing a concentrated infusion of 
opium with a solution of chloride of calcium in excess; ; 
the mixture, when warmed, deposits a precipitate of me- 
conate and sulphate of lime, and the hydrochlorate of mor- 
phia remains in solution. [From this it may be crystal- 
lized by evaporation, and a dark liquor, containing nar- 
cotine and coloring matter, separated by pressure in a 
piece of flannel. ‘The impure hydrochlorate may be re- 
dissolved and re-crystallized, and, by repeating the opera- 
tion, or resorting to animal charcoal, it may be obtained 
quite white. ‘The salt may now be dissolved in hot water 
and acted.on by an excess of ammonia, which throws 
down pure morphia as a white precipitate. It may be 
obtained in crystals by solution in alcohol. 

Morphia is almost insoluble in water; it neutralizes 
acids, and forms crystallizable salts. Its solution is bit- 
ter. It dissolves readily in dilute acids, and yields a deep 
orange-red color when acted on by strong nitric acid. 
The most common of its salts are the hydrochlorate, the 
sulphate, and the acetate. 

Narcotine (C.H,,NO,;) 1s associated with morphia in 
opium. It may be obtained by digesting the insoluble 
portion with dilute acetic acid; the precipitate produced 
by ammonia is to be dissolved in alcohol, and purified by 
animal charcoal. It yields prismatic crystals, insoluble in 
water, and is a weak base. By the action of peroxide of 
manganese and sulphuric acid, and by bichloride of plati- 
num, it yields an extensive series of bodies, some of which 
are Acide and others bases. 

Codeine (C3;Hy)NO;).—The hydrochlorate of morphia, 
prepared as above described, contains this base; and when 
the precipitation with ammonia is made it remains in so- 
lution. When pure, it crystallizes in octahedrons, and is a 
powerful base. Along with this body, in opium there oc- 
casionally occur other substances of less importance, as 
Thebaine, Pseudomorphine, Narceine, and Meconine. 


From what is morphia obtained? When was it discovered? Give a 
process for its preparation. How is narcotine prepared? What are its 
properties? What other alkaline bodies are obtained from opium ? 


QUINA.—CINCHONA. 369 


Meconic Acid (C,,1O,,, 3HO).—A tribasic acid, asso- 
ciated with morphia in opium. It may be obtained from 
the meconate of lime, which precipitates in the prepara- 
tion of morphia by mixing it with warm dilute hydro- 
chloric acid, and repeating the operation until all the 
lime is removed. When purified from coloring matter, it 
crystallizes in scales, which are soluble in water and al- 
cohol. When heated, it loses six atoms of water of crys- 
tallization; and if its solution be boiled, or the dry acid 
heated in a retort, Comenic Acid, C\,H,O;, 2HO, a brba- 
sic acid forms with the disengagement of water and carbon- 
ic acid. Meconic acid yields, with the persalts of iron, a 
blood-red solution. It forms several series of salts, like 
all tribasic acids. | 

Comenic acid, when heated, yields carbonic acid and a 
new body, Pyromeconic Acid, with a small quantity of an- 
other substance, parameconic acid. Pyromeconic acid is 
composed of C,,—,0;, HO. 

Quina—Quinine (CyH,,NO,).—This, which is one of 
the most valuable of the vegetable alkalies, is obtained 
from Cinchona Bark. The decoction of the ground bark 
in dilute hydrochloric acid is to be boiled in an excess of 
milk of lime, and the precipitate acted upon by boiling 
alcohol; on evaporation Cinchona is deposited in crystals, 
but the quina remains in solution. It may be precipitated 
by the addition of water, and obtained in crystals from 
the spontaneous evaporation of its solution in absolute al- 
cohol. Quina neutralizes acids perfectly, giving rise to 
salts, of which the hydrochlorate, phosphate, sulphate, 
&c., are employed in medicine. It is sparingly soluble 
in water, but very soluble in alcohol or acids. The basic 
sulphate of quina, a common preparation, is sparingly sol- 
uble in water, but the neutral sulphate is much more so. 
For this reason, sulphate of quina is often dissolved in di- 
lute sulphuric acid. 

Cinchona (C\,f,,NO).—This alkali is obtained, as just 
stated, in the preparation of quina, with which it is asso- 
ciated in bark, and is found in large quantity both in the 
gray and red bark. It crystallizes in prisms, is sparing- 


How is meconic acid procured? What is the action of heat upon it? 
W hat color does meconic acid yield with persalts of iron? Whencomenic 
acid is heated, what acids does it yield? From what source is quina de- 
rived? How is cinchona prepared ? 


370 STRYCHNIA.—BRUCIA. 


ly soluble in water. Its salts, like those of the foregoing, 
are very bitter. 

Two other analogous bodies exist in different species 
of bark. They are Chinoidine and Aricine. 

Kinie Acid ( C,,H,,O,,, HO) is associated with the fore- 
going bodies in bark. It is obtained by decomposing the 
kinate of lime, obtained in the manufacture of sulphate of 
quina by oxalic acid, filtering the solution from oxalate 
of lime, and the kinic acid crystallizes on evaporation. It. 
is very soluble in water. 

Strychnia (C,,H,,N,O,) occurs in Nux Vomica, St. Ig- 
natius’s Bean, in the poison Upas Tieute, and other vege- 
table products. It may be extracted from nux vomica 
seeds by boiling them in dilute sulphuric acid, and then 
acting with lime and alcohol as described in the case of 
quina. 

Strychnia requires 7000 parts of water for solution, and 
communicates to it an intensely bitter taste. It is one of 
the most violent poisons known. Its alkaline powers are 
well defined, and it produces a complete series of salts. 
It is soluble in hot alcohol, but not in ether. The anti- 
dote for an over-dose of it is an infusion of tea. 

Brucia (C,,H,,N,O;) is ‘associated with strychnia, and, 
being very soluble in cold alcohol, is readily separated 
from it. It is also more soluble in hot water, and pos- 
sesses the poisonous character of strychnia. These sub- 
stances are found in union with Igasuric Acid. 

The following table gives the names of other vegetable 
alkalies, and bodies analogous to them : 


Aconitine. Daturine. Picrotoxine. 
Antearine. Delphinine. Piperine. 
Asparagine. Elaterine. Phloridzine. 
Atropine. Emetine. Populine. 
Caffeine—Theine. Gentianine. Salicine. 
Chelidonine. : Hesperidine. Solanine. 
Chinoidine. Hyosciamine. Stramonine. 
Colchicine. Meconine. Thebaine. 
Conine. Narceine. Theobromine. 
Curarine. Narcotine. Veratrine. 
Daphnine. 


Of some of these bodies, as nicotine and conine, it may 


What other alkalies exist in bark? With what acids are these bodies 
associated? From what sources is strychnia procured? What are the 
properties of strychnia? What is the best antidote to its poisonous ef- 
fects? With what other alkali is it associated? Mention some other 
vegetable alkalies. 


wg 


COLORING BODIES. sil 


be remarked that they are volatile oily liquids, which can 
form crystallizable salts and acids. They both contain 
nitrogen, and are interesting in their relations to the three 
following bodies, which may be formed artificially. 

Aniline (C,,H,N).—This substance is formed by the ac- 
tion of potash on isatine, and is also one of the ingredi- 
ents of the oil of coal tar. It is an oily liquid, boils at 
358°, and yields crystalline salts with acids. 

Leukol (C,;H;N).—Formed with the foregoing in oil of 
coal tar, from which it may be separated by distillation. 
It is also an oily liquid, and can yield crystallizable salts. 

Quinoline (C\,H,N).—Formed by distilling quinine or 
strychnine with caustic potash. An oily liquid, very bit- 
ter, strongly alkaline, and yielding crystallizable salts. 

Besides these bodies there are other artificial bases of 
an analogous nature, but which differ in the remarkable 
particular’ of containing platinum and arsenic; such, for 
example, as the platina bases of Reiset and Gros, or the 
arsenico-platinum radical kakoplatyle. The formation of 
these organic bases leads us to hope that the vegetable 
alkalies themselves will hereafter be artificially formed. 


LECTURE LXXXIIl. 


Tue Cortorine Bopres.— General Properties of Color- 
ing Principles. — Madder.— Hematoxryline.— Cartha- 
mine.— Yeliew Colors. — Chlorophyll.— Indigo.—Sul- 
phindigotic Acid. — Deoxydized Indigo.— Action of 
Heat and Reagents on Indigo.— Litmus.— Carmine. 


Tue coloring principles derived from the organic king- 
dom may be conveniently divided into two classes: the 
non-nitrogenized and the nitrogenized. They may also 
be readily classed into groups, as blue, red, yellow, green. 
For the most part they are derived from vegetable pro- 
ductions. 

For some coloring matters the fibres of those tissues 
commonly employed for clothing have a sufficient affinity 
as to hold the color so that it can not be removed by mere 


What analogous substances have been formed artificially? What may 
be remarked as respects the salts of Reiset and Gros? How may color- 
ing principles be classified ? 


37z NON-NITROGENIZED COLORS. 


washing, and is permanently dyed. But in other in- 
stances this is not the case; the artist then has to avail 
himself of the qualities possessed by intermediate bodies, 
such as alumina and the oxide of tin, which at once pos- 
sess the double quality of an affinity for the coloring mat- 
ter and an affinity for the cloth fibre. The attraction of 
these bodies for coloring matter may be illustrated ,by 
precipitating alumina in a solution tinged by litmus; the 
solution becomes perfectly clear, its color going down 
with the precipitate, and forming with it a lake. 


NON-NITROGENIZED COLORING MATTERS. 

The Blue non-nitrogenized coloring matters are chiefly 
found in flowers and fruits. They are reddened by acids, 
and turned green by alkalies. 

The Red non-nitrogenizing coloring matters are of 
some importance; among them may be mentioned Mad- 
der Red, the sublimed crystals of which are known as Alz- 
zarine (Oy,H,,O\). Madder also furnishes a purple and 
a yellow color. 

Heaematoxyline (CyH,,O,;) is the coloring matter of log- 
wood; it is soluble in water and alcohol, and furnishes, 
with iron salts, the black dye for hats. The same princi- 
ple is yielded by Brazil-wood and cam-wood. Cartha- 
mine is a very beautiful red, obtained from safflower; it 
is used for making pink saucers. 

The Yellow coloring matters. Among these may be 
mentioned Quercitrine (C\,H,O,, H{O), derived from the 
Quercus Tinctoria ; Gamboge, the dried juice of the Gar- 
cina Gambogia ; Turmeric, used as a test for alkalies, 
which turn it brown, from the Curcuma Longa; and 
Anatto, from the seeds of the Bixa Orellana. 

The Green coloring matters: Chlorophyll, the constitu- 
tion of which is not known. It is the green coloring mat- 
ter of leaves. It is insoluble in water, but soluble in al- 
cohol and ether, and is a fatty substance. It is also found, 
under very interesting circumstances, in the animal sys- 
tem as the coloring matter of bile. 


From what source are the blue non-nitrogenized colors obtained? What 
is alizarine? What are hematoxyline and carthamine? From what 
sources are quercitrine, gamboge, turmeric, and anatto derived? What is 
chlorophyll ? 


INDIGO. 313 


NITROGENIZED COLORING MATTERS. 

The nitrogenized coloring matters, among which are 
some of the most valuable dyes that we possess, may also 
be divided according to their tint. 

Indigo is derived from the juice of several species of 
Indigofera, and is formed from a colorless or yellow com- 
pound which is dissolved out from the leaves of these 
plants when they are allowed to ferment with water. <A 
deep blue precipitate (indigo) forms. It appears, there- 
fore, to be a product of oxydation. It comes in com- 
merce in small masses, which, when rubbed, exhibit a 
coppery aspect, is insoluble in water, alcohol, dilute 
acids, and alkalies, and may be sublimed, yielding a pur- 
ple vapor, which condenses into crystals of pure. indigo. 
It dissolves in about fifteen parts of strong sulphuric acid, 
but still better in Nordhausen oil of vitriol, yielding a 
mass which is soluble in water. It is Sulphindigotic Acid. 
By contact with deoxydizing agents, blue indigo becomes 
colorless, as may be shown by digesting powdered indigo, 
green vitriol, hydrate of lime, and water together. In 
this state, as in its natural condition, it is soluble in wa- 
ter, and white indigo may be precipitated by hydrochloric 
acid. On exposure to the air, deoxydized indigo absorbs 
oxygen rapidly, and becomes blue and insoluble. 

When indigo is submitted to destructive distillation it 
yields -an oily liquid, Anz/ine, possessed of powerfully 
basic properties, and described in the last Lecture. 

The relation which exists between blue and white indi- 
go is seen from their formulas. 

Blad indigo } “fs. O7.) us. eee CighNOs 
White-indieo™. ir. 2) os ha Cre HeNOe 

By several chemists indigo is regarded as containing a 
radical, Anyle, = C,,H,N, the symbol for which is Az. 
On this view, blue indigo is the anhydrous deutoxide of 
anyle, AnO,, and white indigo the hydrated protoxide, 
AnO, HO. 

Under the action of heat and of reagents, indigo yields 
an extensive class of bodies, to which much attention has 
been given. In this place I can do little more than enu- 
merate some of them. With dilute nitric acid it yields 


From what source is indigo derived? Howissulphindigotic acid made ? 
What is deoxydized indigo? How is aniline made? What is the rela- 
tion between blue and white.indigo? What is anyle? 


I 


374 LITMUS.—CARMINE. 


Anilie or Indigotic Acid. With strong nitric acid it yields 
Picric or Carbazotic Acid, a substance of a yellow color, 
bitter taste, and forming explosive salts. Heated. with 
bichromate of potash, sulphuric acid, and water, it yields 
Isatine, which crystallizes in red prismatic crystals, and 
contains the elements of blue indigo, with two additional 
atoms of oxygen. This body, under the influence of an 
alkaline solution, unites with one atom of water, and 
changes into Isatinic Acid. Under the influence of chlo- 
rine, isatine yiclds Chlorisatine, by an atom of chlorine 
substituting one of its hydrogen atoms, and Bichlorisatine, 
by the substitution of two chlorine atoms for two hydro- 
gen ones; and these, again, as in the case of isatine itself, 
acted upon by alkaline solutions, yield each an acid. 
Caustic alkalies, acting on indigo, yield Crysanilic and 
Anthranilic Acids. 

Litmus is derived from the Rocella Tinctoria, Lecanora 
Tartarea, &c. These lichens yield to ether a crystalline 
substance, to which the name Lecanorine is given. It 
does not contain nitrogen. It is in white crystals, soluble 
in hot alcohol and ether. This substance, heated with 
baryta or alkalies, yields Orcine, by losing two atoms of 
carbonic acid. Orcine crystallizes in prisms, which have 
a yellowish tint and asweet taste. Mixed with ammonia, 
and exposed to the air, oxygen is absorbed, and the hiquid 
assumes a deep purple tint. From this acetic acid precip- 
itates a deep-red powder, Orceine, C,,H,NO,, which con- 
tains nitrogen, and is supposed to be the visi of the dye 
stuff of litmus. With alkalies it gives a blue color. Lit- 
mus is extensively used in chemistry as a test for acids 
and alkalies. 

Carmine is the coloring matter of the cochineal insect, 
Coccus Cacti. The coloring matter may be obtained from 
the insect by water or ammonia. ‘The carmine of com- 
merce is a lake containing alumina. 

Aloes is the inspissated juice of certain species of Aloe, 
used as a purgative medicine. When heated with nitric 
acid, and water added, a yellow precipitate is thrown 
down, which, when purified, is Chrysammic Acid. It 


What are indigotic acid, carbazotic acid, andisatine? What is the effect 
of alkaline solutions on isatine? What is the effect of chlorine upon it ? 
From what sources is litmus derived? What are orcine and orceine ? 
From ganas source is carmine derived? How is chrysammic acid pre- 
pared ? 


THE FATTY BODIES. 375 


yields yellow crystals of a bitter taste, and furnishes a 
solution of a purple color. Its salts are crystallizable, by 
transmitted light of a red color, with a green metallic re- 
flection like murexide. The liquid from which this acid 
was precipitated contains picric acid. 


LECTURE LXXXIV. 


Tur Farry Boptes.—Properties of the Saponifiable Fats. 
—Distinction between Fixed and Volatile Oils——Prep- 
aration of Soaps.—Stearine and Stearic Acid.— Mar- 
garine and Margaric Acid.—Oleine and Oleic Acid.— 
Margarone-—Production of Glycerine—-Natural Oils, 
as Palm Oil, Cocoa Tallow, and Nutmeg Butter.— 
Spermaceti.—Cholesterine— Three Classes of Volatile 
Oils.— The Camphors. 


Turs class of substances is characterized by several 
well-marked peculiarities, and may be conveniently di- 
vided into two natural groups, oils and fats. They belong 
both to the vegetable and animal systems. In the former 
they usually abound in the seeds or fruits; in the latter 
they are deposited in the cellular structure of the adipose 
tissue. The natural fats are usually mixtures of two or 
more ingredients, which differ from one another in con- 
sistency. In most instances they are stearine and mar- 
garine, along with a liquid oleine. The oils can not be 
distilled without undergoing decomposition ; exposed to 
the air, they gradually absorb oxygen and evolve carbonic 
acid. Many of them, in which this change takes place 
with rapidity, turn into resinous bodies ; and hence their 
application, in the art of painting, as drying oils. When 
acted upon by alkalies, the fixed oils and fats give rise to 
soaps, and hence are spoken of as Saponifiable. 

Oily bodies may be divided into fixed and volatile. 
The fixed oils decompose when heated ; the volatile ones 
distill. A simple test, therefore, is sufficient to distinguish 
them. When a few drops of an oily substance are put on 
paper, if it be a volatile oil it soon evaporates, and leaves 


Into what natural groups may the fatty bodies be divided? "What are 
the natural fats? What change do the drying oils undergo? How may 
the fixed oils be distinguished from the volatile ? 


376 SAPONIFICATION. 


the paper without a stain; if fixed, the paper remains 
greasy. The fixed oils have but little odor, the volatile 
oils commonly a characteristic one. ‘They are all insol- 
uble in water; many of them are soluble in alcohol; but 
in ether they are freely dissolved. 

By exposure to a low temperature the constituent prin- 
ciples of a mixed oil may often be separated from each 
other, the more solid substances separating as the tem- 
perature descends. When olive oil is thus treated, an 
exposure of 40° IF. causes a deposit of Margarine: the 
fluid portion which is left is Olezne. Animal fats exposed 
to pressure between folds of blotting paper communicate 
to it oleine, and the solid residue which is left behind is a 
mixture of margarine and Stearine. When the fixed fats 
are boiled with alkaline solutions, Soaps are formed ; 
these substances, which are of extensive use in domestic 
economy and the arts from their detergent qualities, are 
freely soluble in water. In the process of making them, 
the fats undergo a change; they form true acids, stearine 
yielding stearic acid, margarine margaric acid, and oleine 
oleic acid, which may be set free by decomposing the 
soap with an acid. With them there is also formed a 
sweet substance, Glycerine, which appears to be the same, 
whatever fat may have been originally employed. Of 
the varieties of soap met with in commerce, Soft Soap is 
made from potash, combined with whale or seal oil; Hard 
White Soap from tallow and caustic soda; Hard Yellow 
Soap from soda, tallow, palm oil, and resin. In the prep- 
aration of white soap the alkaline solution is made to boil, 
and tallow added in small portions until no more can be 
saponified ; the solution now contains soap and free gly- 
cerine; the former is separated by the addition of com- 
mon salt, in a solution of which it is insoluble. It floats 
on the top of the liquid. It is then run into moulds, and 
cut into bars for commerce. In this process the manu- 
facturer does not add so much salt as to separate all the 
water. Commercial soap still contains from 40 to 50 per 
cent. 

Stearime may be obtained from purified mutton fat by 


W hat is the difference of their properties? What is the effect of a re- 
duction of temperature on mixed oils? Into what may olive oil be thus 
decomposed? What are soaps? How may the different varieties ‘be 
formed? How is stearine prepared, and what are its properties ? 


STEARIC AND MARGARIC ACIDS. bs We | 


suffering a warm ethereal solution to cool. The stearine 
crystallizes, and margarine and oleine are left in solution. 
A repetition of the process purifies it. It is a white body, 
insoluble in water and in cold alcohol. It melts at 130°, 
When saponified, it yields glycerine and stearic acid. 

Stearic Acid ( Cost ¢5 Os) may be crystallized from a hot 
alcoholic solution, is insoluble in water, and without taste 
or smell. It is ableble both in Bleach and ether, melts 
at 158°, and may be volatilized without. change. 

Margarine.—'This substance remains with oleine in the 
ethereal solution arising in the preparation of stearine, 
and may be obtained from it by evaporation and pressing 
the soft mass in paper. Margarine is found more abund- 
antly in human than in other kinds of fat. 

Margaric Acid (C,;f,O;) 1s prepared by saponifying 
margarine with potash and decomposing with hydrochlo- 
ric acid. It is also formed with other products by the 
distillation of stearic acid. It crystallizes in white nee- 
dles, its melting point being 140°. 

Oleine—W hen almond or rape oil is dissolved in ether 
and the solution exposed to a low temperature, the mar- 
garine crystallizes, and oleine may be obtained by evap- 
orating the ether. It remains liquid at a temperature of 
0°. From it Oleze Acid (C,,Hj,0,) may be obtained by 
saponification and decomposition with muriatic acid, as in 
the for egoing instances. Its melting point is about 20°. 
It gives rise to a class of salts. 

Margarone ( Cec-Ldee O> )— When a mixture of margaric 
acid and lime is distilled this substance is formed, and 
carbonic acid separates. It is a white solid, like sperma- 
ceti, and melts at 170°. 

Glycerine (C,H;O,).—This substance arises when any 
fatty matter is saponified with potash, the soap being de- 
composed with tartaric acid, and dissolving the glycerine 
out by alcohol. It is a colorless liquid, specific gravity 
1:26; it is soluble in water and alcohol, but not in ether. 
It may be cooled to a very low point without assuming 
the solid form. When mixed with sulphuric acid, the 
two bodies unite directly, and Sulphoglyceric Acid is 


What is the process for preparing stearic acid? How are margarine 
and margaric acid obtained? What are the properties of oleine? How 
is oleic acid made?) What is margarone? Under what circumstances 
does glycerine form ? i 

I2 


378 FATTY BODIES. 


the result: an acid having many analogies with sul- 
phovinice. ° 

Paim Oil is brought from Africa, and much of it used 
in the manufacture of yellow soap. It is of a reddish- 
yellow color, and contains, besides oleine, a solid fat, Pal- 
mitine. It is insoluble in water, slightly soluble in hot al- 
cohol, but very soluble in ether.’ Its melting point is 118°. 
By saponification and decomposition with an acid, it yields 
Palmitic Acid, the melting point of which is 140°. It is 
a bibasic acid. 

Cocoa Tallow.—A solid fat obtained from the cocoa- 
nut, and used in the manufacture of candles. Its oleine 
and stearine may be separated by pressure, or by boiling 
alcohol, from which the stearine crystallizes on cooling. 

Among other fatty substances and allied bodies may 
be mentioned Nutmeg Butter, which yields, among other 
products, Myristicine, and by saponification, Myristic Acid. 
Elaidine, which arises from the action of nitrous acid on 
oleine ; it furnishes, by the common process, Elazdic 
Acid. Suberic Acid, which arises from the action of nitric 
acid on cork. Swuccinic Acid, by the destructive distilla- 
tion of amber, or by the continued action of nitric on 
stearic acid. Sebacic Acid, by the destructive distilla- 
tion of oleic acid. Butyrine, Caproine, and Caprine, 
which are contained in butter. These yield, by saponifi- 
cation and decomposition, Butyric, Caproic, and Capric 
Acids. Butyric acid can be made, as we have seen, ar- 
tificially by fermentation. Bees’ Wazx is a mixture of two 
bodies: Cerime, which may be dissolved by boiling alco- 
hol, and Myricine, which is insoluble therein. Spermaceti, 
which is obtained from certain species of whales, yields, 
under the process for glycerine, a substance, Hthal, and 
this, under the action of hot potash, gives Hthalic Acid, 
with evolution of hydrogen gas. Cholesterine is obtained 
from biliary calculi; it also occurs in the substance of the 
brain. 

Tue Vouatite O1rs.—These, for the most part, are 
found in plants, or are derived from them by simple proc- 
esses. Many of them are extensively used in the arts in the 


What are palm oil, palmitine, and palmitic acid? Mention some other 
bodies belonging to the same class. rom what are suberic, succinic, and 
sebacic acids derived? What bodies are contained in butter, and what 
acids do they yield? What two substances are found in bees’ wax? 
From what are spermaceti and gga derived ? 

D 


VOLATILE OILS. 379 


manufacture of varnishes, and others in the preparation 
of perfumery. ‘Their solutions in alcohol form Essences, 
and in water Medicated Waters. ‘They are commonly 
obtained by the distillation of those parts of the plants in 
which they occur, with water, and consist of two substan- 
ces, a solid portion, Stearopten, or camphor, and a true oil. 
They may be divided into groups according to their con- 
stitution. 
Volatile Oils containing Carbon and Hydrogen. 


Turpentine. Bergamotte. 
Citron. Cubebs, 
Copaiva. &e. 
Storax. 

Volatile Oils containing Carbon, Hydrogen, and Oxygen. 
Cajeput. Pennyroyal. 
Lavender. Valerian. 
Rosemary. Spearmint, 
Peppermint. &e. 

Volatile Oils containing Sulphur. 
Black mustard. Onions. 
Horseradish. Asafetida. 


The stearoptens (camphors) of the volatile oils are best 
represented by common camphor, which is extracted from 
the Laurus and Dryabalonops Camphora by distilling with 
water. It is a white, tough, semitransparent mass, light- 
er than water, of a well-marked odor, melts at 350°, and 
soon after sublimes rapidly unchanged. Artificial Cam- 
phor is made by passing dry muriatic acid gas into oil of 
turpentine. It is a muriate of oil of turpentine. The 
true camphors originate in several different ways ; some- 
times by the oxydation of the oils from which they are 
derived; sometimes they are hydrates of those oils; and 
sometimes they are isomeric with them. 


Into what groups may the volatile oils be divided? What are the cam- 
phors? What is common and artificial camphor? 


380 RESINS.—BALSAMS. 


LECTURE LXXXV. 


Tue Resins, BausamMs, AND BopiEs ARISING IN DeEstRUC- 
tive Distituation.—Colophony, Gum Lac, Amber, &c. 
—India-rubber—Bausams.— Products of the Destructive 
Distillation of Wood.—Paraffine, Eupione, Creasote, and 
allied Bodies —The Destructive Distillation of Coal._— 
Naphthaline, Paranaphthaline, Kyanol, Carbolic Acid. 
— Products of slow Decay— Ulmine and Ulmic Acid.— 
Crenic and Apocrenic Acitd.— The Varieties of Coal and 
other subsidiary Bodies. 


THE resins are bodies in many respects analogous to 
the camphors, but are distinguished from them by the cir- 
cumstance that they are not volatile without decomposi- 
tion. In many instances they act as acids; they all con- 
tain oxygen. 

Colophony is a raixed resin, obtained by the distillation 
of turpentine with water, the oil of turpentine passing over. 
It is a mixture of two resins, Pinic and Sylvic Acids, which 
may be separated by cold alcohol, in which sylvic acid is 
insoluble. 

Gum Lac, which is one of the resins, occurs under three 
forms: shell lac, stick lac, and seed lac. It is used in the 
preparation of lacquers, and is the chief ingredient in seal- 
ing-wax.. Among other resins may be mentioned Copal, 
Mastic, Dragon's Blood, Gamboge, Sandarac, and Dam- 
mara Resin. 

Amber is asubstance belonging to this class. It is form- 
ed in beds of bituminous wood, and often incloses insects 
ia a state of beautiful preservation. Its specific gravity 
is about 1:07. By distillation it yields succinic acid. 

Caoutchouc — Indian-rubber, or Gum-elastic —is the 
product of the Jatropa Elastica, the Hevea Caoutchoue, and 
several other tropical trees. The milky juice which they 
yield is dried on moulds of various forms; it turns of a 
black color by being smoked. [rom its imperviousness 


What are the resins? What substances may be obtained from coloph- 
ony? What is gum lac? What acid does amber yield by distillation ? 
irom what sources is India-rubber derived? What is the cause of its 


black color ? 


DESTRUCTIVE DISTILLATION. 381 


to water, this substance has of late been introduced for a 
great variety of purposes. It is combustible, burns with 
a bright flame, is softened by boiling water, and still more 
so by ether. In ether, as also in naphtha and coal oil, it 
may be dissolved. Bags of it, soaked in ether until they 
become gelatinous, may be distended, by blowing into 
them, to a very great size, and thus become useful for a 
variety of purposes. Very few chemical agents act upon 
India-rubber: it is extensively used for connecting the 
parts of chemical apparatus. 

Batsams are compounds of resins with volatile oils ; 
some of them also contain benzoic or cinnamic acids. 
Some, as benzoin, are solid; and others, as the Balsams 
of Tolu and Peru, are viscid fluids. 


THE PRODUCTS OF THE DESTRUCTIVE DISTILLATION OF 
WOOD? &c- 


When wood is submitted to distillation in close vessels, 
a black, inflammable liquid called Tar is formed ; it con- 
tains a great many remarkable bodies, among which the 
following may be mentioned. The solid black residue 
which is left after the distillation or inspissation of tar 
constitutes Pztch. 

Paraffine (C.H) is obtained by distilling tar, several 
oils coming over: itis from the heaviest that this substance 
is extracted. It is a solid substance, lighter than water, 
of a fatty appearance; it melts at 111° FE, and distills 
unchanged. Few chemical agents act upon it: it remains 
unchanged by the alkalies, acids, &c., but is soluble in 
turpentine and naphtha. [rom its chemical indifference 
it has obtained its name (Parum Affinis). 

‘Eupione (C,H;) occurs abundantly in animal tar, from 
which it may be prepared by distillation, and subsequent- - 
ly purified by rectification from sulphuric acid. From 
paraffine it may be separated by exposure to cold, or, 
being more volatile, by distillation. It is a colorless li- 
quid, specific gravity .074; it boils at 339° F. It is in- 
soluble in water, but very soluble in alcohol. 

Creasote is extracted from the heavy oil of tar by a 
complicated process. It is an oily, colorless liquid, of a 
burning taste, exhaling a powerful odor of wood smoke. 


— 


How may it be softened, and in what dissolved? What are ohe bal- 
sams? What are tar andpitch? What properties distinguish paraftine ? 
What are the properties of eupione ? 


3882 ° NAPHTHALINE. 


It is slightly heavier than water, boils at 400° F., is com- 
bustible. One hundred parts of water dissolve about 13 
of this substance, and obtain its peculiar odor. It has the 
remarkable property of coagulating albumen and preserv- 
ing flesh from putrefactive changes. Irom this latter cir- 
cumstance its name is derived. 

Among allied substances may be mentioned Picamar, 
an oily liquid of a bitter taste, which boils at 518° F’., and 
combines with bases to form crystalline compounds. ap- 
nomar, a colorless liquid, having an odor of rum; boils at 
360° F., and forms, with oil of vitriol, a purple solution. 
Cedriret, which forms red crystals, giving, with creasote, 
a purple solution, and with sulphuric acid a blue. Petta- 
kal, a dark blue solid, which yields blue precipitates with 
metallic salts. It contains nitrogen. 

When coal tar is submitted to distillation, like wood 
tar, it yields a volatile oil, which, by being submitted to 
rectification, becomes Coal Oil, or Artificial Naphtha. 
Irom it a variety of substances may be extracted; they 
either pre-exist in the oil, or are formed by the operation. 

NapuTuatine (C,,f,) is obtained by rectifying coal 
gas tar; it forms colorless crystalline plates, melting at 
136° EF. and boiling at 413° F. It exhales a peculiar 
odor, is very combustible, insoluble in water, but soluble 
in ether and alcohol; the specific gravity of its vapor is 
4°528. It dissolves in sulphuric acid, and the solution, on 
being diluted with water and saturated with carbonate of 
baryta, yields two salts, one containing Sulphonaphthalic 
Acid, and the other an acid less known. 

Paranaphthaline ( C,;H,;) is associated with naphthaline, 
but differs from it by being insoluble in alcohol, by which 
liquid they may, therefore, be separated. 

Kyanol (C,,H,N), an oily liquid, which, though volatile, 
has a boiling point of 358° I’. It is heavier than water, 
with which it-may be combined, and is soluble in alcohol 
and ether. It possesses basic properties, and yields sev- 
eral well-defined salts. 

Carbolic Acud—Hydrate of Phenyle ( C,,H,O)—is found 
in that portion of oil of tar which boils between 300° F. 


What remarkable properties does creasote possess? From what is its 
name derived? From what sources are picamar, kapnomar, cedriret, and 
pittakal obtained? What are the properties of naphthaline 1 What sub- 
stance closely resembles it? What are the properties of kyanol ? 


BODIES PRODUCED BY DECAY. 3883 


and400° F. This being agitated with potash, and the re- 
sult decomposed by an acid, yields carbolic acid, which 
may be purified by rectification from caustic potash, It 
is an oily liquid, but may be -obtained in long, needle- 
shaped crystals. A splinter of pine wood first dipped in 
it and then in strong nitric acid becomes of a blue color, 
which then passes into a brown. In many particulars 
this substance resembles creasote so closely, that a suppo- 
sition has been entertained that they are in reality the 
same body. 

When woody matter is gradually decomposed by con- 
tact with air and moisture, Ulmine and Ulmic Acid are 
produced. They arise from a partial oxydation, attended 
by the production of carbonic acid and water, the action 
being originally occasioned by azotized matter in the 
wood ; corrosive sublimate, or any other body which pos- 
sesses the quality of checking ferment action, may, there- 
fore, be resorted to to prevent the dry-rot of wood. When 
the access of air is, for the most part, cut off, the brown 
bodies, ulmine and ulmic acid, no longer appear alone, 
but with them many other substances, of the family of the 
hydrocarbons, arise. Besides these, as in the formation 
of vegetable soil and turf, azotized acids, such as the Cren- 
tc and Apocrenic, appear. These originate in the decay 
of the nitrogenized constituents of the wood, an action 
which probably precedes its general disorganization. 
They are often found in mineral springs, in combination 
with oxide of iron, forming ochery stains. Crenic acid, by 
exposure to the air, changes into Apocrenic Acid, a sub- 
stance much less soluble in water. 

There is abundant proof that all the varieties of coal 
have originated from woody fibre. or the production of 
these, it seems requisite that the wood should be immers- 
ed in water at a moderately high temperature, and with- 
out free contact of air. The ulmine bodies form from the 
decay of wood at the surface of the earth; the coal bod- 
ies under a heavy pressure. Of these we have many va- 
rieties, differing much in constitution: Lzgnite, which is 
of a brown color, and in which the structure of the wood 

What substance does carbolic acid closely resemble? Under what cir- 
cumstances are ulmine and ulmic acid produced? What bodies may be 
employed to prevent dry-rot? From what bodies do crenic and apocrenic 


acids arise ? What is the source of the different varieties of coal? What 
is lignite ? 


384 ANIMAL CHEMISTRY. 


is more or less perfectly preserved ; the various forms of 
Bituminous Coal, as cannel coal, Newcastle coal, &c.; An- 
thracite, which contains but little hydrogen. 

With these more valuable natural products are frequent- 
ly found small quantities of others of less importance, as 
Ozocherit, or fossil wax ; Idrialine, which is isomeric with 
oil of turpentine ; Petroleum, or Naphtha, which in many 
Eastern countries is collected in wells. It arises, proba- - 
bly, from the decomposition of coal by the action of the 
natural heat of the earth. 


LECTURE LXXXVI. 


ANIMAL CuEemistRY.— Equilibrium of the System.— Caus- 
es of Diminution and Increase.—felation of Oxygen to 
the Food.— Digestion, the Nature of at.—Description of 
the Process. Artificial Digestion.— Two great Varieties 
of Food.— Nutrition in the Carnivora and Graminivora. 
—Routes of the Passage of Nutritious Matter into the 
System. 


In the preceding Lectures I have given the descriptive 
history of many of the more important organic compounds, 
and chiefly those belonging to, or derived from, the vege- 
table kingdom. It remains now to mention another class 
which seems to bear a closer relation to animal beings. 
The appearance and destruction of these compounds lead 
by ready steps to a consideration of the physiological func- 
tions of the animal mechanism. 

There are certain causes which tend constantly to change 
the weight of an adult, healthy individual ; causes of in- 
crease and causes of diminution. Among the former may 
be mentioned food, drinks, and atmospheric air; among 
the latter, urine, fascés, transpired and expired ‘haters. 
And these, i in the course of a year, amount to many hun- 
dred pounds; yet the resulting action of the mechanism 
is such that, at the end of that time, the weight remains 
unchanged. 

This fact, the constancy of adult weight, can, therefore, 
only be explained by an examination of the action of the 


What causes are in operation tending to change the weight of an adalt 
animal? Mention some of the causes of increase, and some of diminution. 


PROCESS OF DIGESTION. 385 


matters introduced into the interior of the system on each 
other, or an examination of the matters rendered. What- 
ever is fit for food, when burned in the open air, with free 
access of oxygen, must yield carbonic acid, water, and 
ammonia; and these, in point of fact, are the results of the 
action of the animal mechanism. Oxygen gas, introduced 
by the respiratory process through the lungs, effects event- 
ually the destruction of the hydrocarbons and nitrogenized — 
bodies which have been introduced through the stomach ; 
and carbonic acid, ammonia, and the vapor of water, or 
substances in a transition state, which tend eventually to 
assume those forms, are the result. An elevated temper- 
ature must, as a consequence, be obtained. 

Before the introduction of chemical principles into the 
science of physiology, it was a favorite idea that the ani- 
mal system possessed the peculiarity of resisting the influ- 
ence of external agents. This is an error. There is no 
essential difference between the physical effects taking 
place in the body during life and after death, nor is there 
any principle of resistance to external agents possessed 
by living structures. The only distinction is, that during 
life the-effete materials pass off by appointed routes—the 
kidneys, the lungs, or the skin; and after death, these 
passages being closed, they accumulate in the interior of 
the body. 

The matters returned by an animal to the external 
world are all found to be oxydized bodies, or such as arise 
from processes of oxydation. The result is, therefore, 
forced upon us that the primitive action of the mechan- 
ism is the oxydation of the food in the system by air which 
has been introduced through the lungs. 

The process of digestion appears to be exclusively for 
the object of effecting the minute subdivision of the food. 
By the action of the teeth or other organs of mastication, 
it is first roughly divided and simultaneously mixed with 
saliva. It is then passed into the stomach, ahd in that or- 
gan mixes with the gastric juice, a viscid and slightly 
acid body. This mixture is perfected by certain move- 
ments which the food now undergoes, and under the con- 


What is the chemical nature of the food? What gas is introduced 
through the lungs? . How do these act on each other? Do animal struc- 
tures possess any power of resisting the influence of external agents ? 
Why do we conclude that the oxydation of the food is the principal effect 
going on in the system? What ne object of digestion ? 


{Ck 


386 PRODUCTION OF CHYLZE. 


joint action of the saliva and the gastric juice it is totally 
broken up into a gray, semifluid, homogeneous mass, 
sometimes acid and sometimes insipid, of the consistency 
of cream or gruel, called Chyme. This gradually passes 
out through the pyloric orifice of the stomach, and enters 
the intestine. 

It has been a question whether artificial digestion could 
be performed, but it now appears to be universally ad- 
mitted that an acidulated water, containing animal matter 
in a state of change, has the power of impressing analo- 
gous changes on organized substances submitted to its ac- 
tion, just as the gastric juice, containing hydrochloric or 
acetic acid, with animal matter undergoing metamorpho- 
sis, derived from the saliva or the coats of the stomach, 
possesses the power of dissolving fibrine or coagulated 
albumen. 

Soon after its entrance into the intestine the chyme is 
mingled with bile and pancreatic juice, the former com- 
ing from the liver, the latter from the pancreas. The ef- 
fect appears to be a division of the chyme into three 
parts: Ist. A creamy fluid; 2d. A whey-like fluid; 3d. 
A red sediment: the two former, commingled, consti- 
tute what is designated the Chyle. 

It has been already remarked that the aim of the di- 
gestive process appears to be the subdivision of the food. 
It is for this that the teeth comminute it; and the gastric 
juice, excited to activity by the oxygen introduced with 
the saliva, breaks down by its ferment action all albumi- 
nous and fibrinous matters, and prepares the food, in this 
condition of extreme subdivision, for its passage into the 
blood-vessels. 

Before we can trace the changes which then occur, it 
is proper, however, to remark that, as respects the food 
itself, it may be distinguished into two varieties: 1st. The 
food of nutgition, or the nitrogenized food; 2d. The food 
of respiration, or the non-nitrogenized food. 

The nutritive processes of carnivorous animals are very 
simple; they live on the graminivora, and find, in the car- 
cases they consume, the fats, the fibrine, and other such 


How is the chyme prepared? Can digestion be conducted artificially ? 
With what fluids does the chyme mingle? What is their action on it? 
What is chyle? What two great varieties of food arethere? Describe 
the nutritive processes of the carnivora. 


ORIGIN OF FAT. 387 


bodies which are necessary for their own economy; these, 
therefore, simply require to be brought into a state of so- 
lution, or of extreme subdivision, and then are absorbed 
into the blood-vessels. In these cases the fats constitute 
the food of respiration, and the nitrogenized bodies that 
of nutrition. 

But the graminivora find in the vegetable matters they 
use the same essential principles; their fibrine, albumen, 
and fats are directly obtained from plants, in which they 
naturally occur. In the digestive process of the two 
great classes of animals, there is not therefore, in reality, 
any difference ; both find in their food the elements they 
require. 

There is reason for believing that the two classes of 
food are introduced into the system by different routes— 
the fatty or respiratory food passing through the lacteals, 
and the nitrogenized bodies being taken up by the veins. 


LECTURE LXXXVII. 


Origin AND Deposits or THE Fars anp Neutrat N1- 
TROGENIZED Bopies.—Artificial Formation of Fat.—It 
may be made in the Animal System, or directly absorbed 
from the Food.—Proofs of the latter Varieties of Fat 
arising in partial Oxydationn—Changes in Fat as it 
passes through the Systems of the Graminivora and 
Carnivora.—TIts final Destruction.— Origin and De- 
posit of the Neutral Nitrogenized Bodies Properties 
of Fibrine, Albumen, Caseine, Proteine, Gelatine, &c. 


Two opinions have been entertained respecting the 
origin of the fat which occurs in the adipose tissues of 
animals. ist. It has been supposed to be produced by 
processes taking effect in the system ; or, 2d. Simply col- 
lected from the food. 

In many various processes fatty bodies arise. Thus, 
when flesh meat is left in a stream of water, a mass of 
adipocire is eventually found. During the action of nitric 
acid on fibrine, and in the preparation of oxalic acid from 

What is their respiratory food? Describe the nutritive processes of the 
graminivora. By what routes are the two varieties of food introduced into 


the system? What opinions have been held respecting the origin of fat ? 
In what processes is it apparently produced ? 


388 ABSORPTION OF FAT. 


starch, oily bodies are apparently produced. There is 
every reason to believe, however, that these are rather 
insulated than formed, or that they pre-exist in the bodies 
from which they are apparently derived. 

But recent experiments, as in the preparation of bu- 
tyric acid from sugar, have decisively demonstrated that 
the fatty bodies can be artificially formed from the non- 
nitrogenized by processes such as those of fermentation, 
and, consequently, we have every reason to suppose that 
the animal system can form fats from the food, although 
none might occur there naturally. 

But though the power of forming oily from amyla- 
ceous bodies may be possessed by the animal mechanism, 
there can be no doubt that in many instances it is not re- 
sorted to, and that fats contained in the food are at once 
absorbed into the system. Often this absorption takes 
place with so slight a change impressed upon the oil, that 
without difficulty we can detect its presence by its odor 
or its taste. Thus, the milk of cows which are fed on 
linseed cake tastes strongly of that substance; and at 
those seasons of the year when such animals feed on 
young shoots or leaves containing odoriferous oils, the 
taste is at once detected in the milk. 

The deposition of fat upon an animal, and the produc- 
tion of butter in its milk, bear a certain relation to the 
amount of oleaginous matters found in its food. For this 
reason, Indian corn, which contains from eight to twelve 
per cent. of oil, furnishes one of the most available arti- 
cles for feeding and fattening cattle. It is now, however, 
admitted that where foods without fat are used, the sys- 
tem possesses the power of effecting their production ; 
thus, bees will produce wax though fed upon pure sugar, 
and animals will grow fat though fed on potatoes alone. 

A great number of the fatty bodies may be derived 
from margaric acid by processes of partial oxydation. 
With a limited supply of oxygen gas, ethalic and myris- 
tic first make their appearance ; and the supply being still 
continued, there follow cocinic, lauric, &c., the process 
being as shown in the following table: 

What reason is there to believe that it can be formed from the starch 
bodies? What reason is there for believing that many fats are directly 
absorbed into the system? Is there any relation between the production 


of butter and the quantity of oil in the food? Can bees form wax from 
sugar? By what process can the fatty bodies be derived from each other ? 


PARTIAL OXYDATION OF FAT. 389 


Margaric. Capric. 
Ethalic. Ginanthytic. 
Myristic. Caproic. 
Cocinic. Valerianic. 
Lauric. Butyric. 


These partial oxydations being perfected, there result at 
last carbonic acid gas and water, the same bodies which 
appear when a fat is directly burned in the open atmos- 
pheric air. ; y 

The fats which occur in plants pass into the systems of 
graminivorous animals, and there undergo changes, a se- 
ries of partial oxydations occurring. It is only a part 
which is completely destroyed so as to produce carbonic 
acid and water, and this part is the element of respiration. 
The residue accumulates in the cells of the adipose tis- 
sues, and, devoured by the carnivorous tribes, is destined 
to undergo in them those successive changes which bring 
it back to the condition of carbonic acid and water, and 
restore it to the atmosphere from which it was originally 
derived by plants. 

The amylaceous bodies and fats, or the non-nitrogenized 
bodies, are, therefore, the food of respiration ;' their office 
is to neutralize the oxygen introduced by the lungs, and, 
by the production of carbonic acid gas and water, keep 
up the temperature of the animal system. 

I have already described the fatty bodies, and given the 
history of their general properties. It is unnecessary to 
repeat here what has been already said. 

When the expressed juices of plants, such as beets, tur- 
nips, &c., are allowed to stand, there is deposited, after a 
short time, a coagulum or clot, which does not appear to 
differ in any respect from animal Fvbrine. If this be remov- 
ed, and the temperature of the juice raised to 212° F., it 
becomes turbid again, from the deposit of a second body, 
Albumen. On separating this and slowly evaporating, a film 
forms on the surface, identical with Caseine. ‘These three 
bodies contain nitrogen, and may, therefore, be looked upon 
as the representatives of the neutral nitrogenized class. 

Fibrine (C3 f5,0,,N; . + (S.P) ).—This substance may 
be obtained by beating fresh-drawn blood with twigs, and 


In what do these partial oxydations terminate at last? What change 
occurs to vegetable fats in passing through the systems of the graminivora? 
What is the object of the entire combustion of a portion of it? By what 
means is the residue at last brought to the same state? What bodies 
constitute the food of respiration? What is the composition of fibrine ? 


K x2 


390 FIBRINE.—ALBUMEN.—CASEINE. 


washing with water and ether the clot which adheres 
thereto. As thus prepared, fibrine is a white, elastic 
body, insoluble in water, alcohol, or ether, but soluble in 
hydrochloric acid, with which it yields a blue solution. 
It possesses the power of decomposing rapidly the deu- 
toxide of hydrogen. When dried it shrinks very much in 
volume, but, for the most part, recovers its bulk when 
again moistened. Fibrine derived from arterial and ve- 
nous blood is not altogether the same ; the latter may be 
dissolved in a warm solution of nitrate of potash, but the 
former can not. In the formula annexed to this body, 
the symbols within the brackets merely mean small and 
indeterminate quantities of sulphur and phosphorus. 

Albumen occurs abundantly in the serum of blood and 
in the white of eggs, from which it may be obtained by 
neutralizing in a solution of it the associated soda with ace- 
tic acid, and on dilution with cold water it falls as a white 
precipitate, soluble in water containing a minute quantity 
of alkali. Exposed to a sufficient heat, common albumen 
coagulates and becomes a white body, wholly insoluble in 
water. ‘The strong acids also unite directly with it, and 
form insoluble compounds; acetic and the tribasic phos- 
phoric acid are exceptions. With metallic salts, as cor- 
rosive sublimate, it gives insoluble precipitates; hence its 
use as an antidote for that poison. Its constitution is iden- 
tical with that of fibrine, except that it appears to contain 
twice as much sulphur. 

Caseine is found abundantly in milk. It is insoluble in 
water, but, like albumen, is readily dissolved if free al- 
kali is present. It may be obtained by coagulating milk 
with sulphuric acid, and dissolving the curd, after it has 
been well washed with water, in a solution of carbonate 
of soda. By standing it separates into two portions, oily 
and watery. From the latter the caseine is re-precipitated 
by sulphuric acid, and the process repeated. The caseine 
is finally washed with ether to remove any trace of fat. 
It is a white substance, soluble in an alkaline water, the so- 
lution not being coagulated by boiling, but a skin forms 
on the surface as evaporation goes on. It can, however, 
be coagulated by certain animal membranes, as by the 


From what sources may it be derived? What are its properties? 
What are the sources and properties of albumen? What are the sources 
and properties of caseine ? 


PROTEINE AND ITS DERIVATIVES. 391 


interior coat of the stomach of a calf. It contains five or 
six per cent. of bone earth. 

The foregoing bodies are sometimes spoken of as the 
PrRoreine group, from the circumstance, as is shown in 
their formula, that they all contain C355 O4No, a body 
which passes under the designation of-proteine. It may 
be extracted from them by dissolving either of them in an . 
alkaline solution, and precipitating by an acid. Itisa 
tasteless, white, insoluble body, soluble in acetic acid 
and in alkalies. It yields a binoxide and tritoxide, which 
may be produced by boiling fibrine in water in contact 
with air. These substances are the chief constituents of 
the buffy coat of inflammatory blood. 

Gelatine (C,;H,,N,O;) is prepared by dissolving isin- 
glass in warm water. It forms, on cooling, a soft jelly, 
which contracts as it dries. Solution of gelatine is pre- 
cipitated by corrosive sublimate, tannic acid, or infusion 
of galls; with the latter bodies it yields a precipitate 
which is the basis of leather. Glue is an impure gelatine. 

On examining the constitution of some of the leading 
tissues of the animal system, it is plain that they bear a 
remarkable relation to proteine, as is shown in the fol- 
lowing table: 

Proteine, CssHseNeOia. . . . = 


Arterial membrane . ee Or Pry 
Chondrine (rib cartilage) a a» 
Hairshorns.) . he i — sl ag 
Gelatinous tissues . . ss = 2Pr SNE Fi ‘O + Ov. 


These different bodies are, therefore, derived from the 
proteine group by processes of partial oxydation ; for in 
their constitution they correspond to oxides, hydrated Ox- 
ides, &c. 

The nitrogenized bodies introduced into the system 
pass through the same changes as the non-nitrogenized : 
partial oxydations giving rise to various tissue forms, and 
ending in perfect oxydation, with a production of water, 
ammonia, and carbonic acid. 

Whether we regard the respiratory or the nutritive 
food, we see that the result is the same. Introduced 
through the blood-vessels into the system, it is brought 


Whatis proteine ? What relation has it to the foregoing bodies? What 
oxides does it give? How is gelatine obtained ? What precipitate does 
it give with infusion of galls? What relation does proteine bear to other 
tissue bodies? What changes do the nitrogenized bodies pass through? 


392 ENTRANCE OF FOOD INTO THE SYSTEM. 


under the destructive influence of oxygen arriving through 
the lungs, and, as I have already explained, the amount 
of oxygen is so adjusted to the amount of these classes of 
food combined, that in an adult and healthy individual the 
weight does not change, even after the lapse of a consid- 
erable period of time. 


LECTURE LXXXVIUII. 


Or THe INTRODUCTION or Respiratory AND Nutritious 
Foop InTo THE BLoon, AND ITs TRANSMISSION THROUGH 
THE SysteEM.—Absorption by the Lacteals and Veins.— 
Cause of the Circulation of the Blood.—Constitution and 
Properties of the Blood — Plasma and Disks.— The Of- 
jices of each.— The Coagulation of Blood.— Analysis 
of Blood. 


Tue ordinary principles of capillary attraction are am- 
ply sufficient to account for the absorption of nutritious 
matter from the mtestinal cavity, both by the lacteal ves- 
sels and the veins. By this it is eventually brought into 
the general current of the circulation, and distributed to 
every part of the system. 

With respect to the forces involved in the circulation 
of the blood, most physiologists have regarded the hy- 
draulic action of the heart as amply sufficient to account 
for all the phenomena. It is now on all hands conceded 
that this organ discharges a very subsidiary duty. The 
whole vegetable creation, in which circulatory movements 
of liquids are actively carried on without any such central 
mechanism of impulsion; the numberless existing acar- 
diac beings belonging to the animal world; the accom- 
plishment of the systemic circulation of fishes without a 
heart; and the occurrence in the highest tribes, as in man, 
of special circulations which are isolated from the greater 
one, have all served to demonstrate that we must look to . 
other principles for the cause of these remarkable move- 
ments. 

The cause of the circulation of the blood is to be found 

What physical principle is involved in the absorbent action of the lac- 


teals and veins? What reasons are there for gare that the action of 
the heart is not the only cause of the circulation ‘ 


CIRCULATION OF ‘THE BLOOD. 393 


in the chemical relations of that liquid to the tissues with 
which it is brought in contact. On the principles of ca- 
pillary attraction a liquid will readily flow through a por- 
ous body for which it has a chemical affinity, but it will 
refuse to flow through it if it has no affinity for it. On 
this principle we can easily explain why the arterial blood 
presses the venous before it in the systemic circulation, 
and why the reverse ensues in the pulmonary. This ex- 
planation of the circulation of the blood, which I offered 
some years ago, is now admitted by many of the leading 
physiological writers to be true. 

The systemic circulation takes place because arterial 
blood has a high affinity for the tissues, and venous blood 
little or none. The pulmonary circulation takes place 
because venous blood has a high affinity for atmospheric 
oxygen, which it finds on the air cells of the lungs, and ar- 
terial blood little or none. Onthe same principle we may 
explain the rise of sap in trees, the circulatory movements 
in the different animal tribes, and the minor circulations 
of the human system. 

The most striking peculiarity of the blood is the inces- 
sant change which it undergoes. It is constantly being 
destroyed, and as constantly being reproduced. It con- 
sists of two portions, the Plasma, a clear fluid, of a yellow- 
ish tinge, which contains fibrine, albumen, and fat; and 
in this there float disk-like bodies of different shapes and 
magnitudes in different animals. In man they are about 
<vaz of an inch in diameter, consist of a sac of Glodbuline, 
a body of the proteine family, and in the interior they con- 
tain a red substance, Hematine, which gives them their 
peculiar color. On one portion of them there is a nucle- 
us or speck, consisting of coagulated fibrine. When the 
disks are old and about to be destroyed, their interior is 
filled with Hemaphein, a yellow substance, correspond- 
ing to the coloring matter of the urine. Besides these, 
there are lymph, chyle, and oil globules in the blood. 

A continuous metamorphosis goes on during the circu- 
lation of the blood; the plasma serves for the purposes 


What explanation may be given of the circulation in the capillaries ? 
What is the cause of the systemic circulation? "What ofthe pulmonary ? 
Of what parts is the blood composed? What are the properties of the 
plasma? Of what are the disks composed? What are globuline, hema- 
tine, and hemaphein? What are the functions of the plasma and disks 
respectively ? 


, 


> 


394 COAGULATION OF BLOOD. 


of nutrition, the disks for the production of heat. They 
absorb oxygen in the air cells of the lungs, and transmit 
it to all parts of the system; and as they grow old and 
disappear, new ones are formed from the plasma. 

Although fibrine is known to exist in plants, I doubt very 
much whether it is directly absorbed as Fibrine into the 
system. Besides the direct proof which we have from 
the analysis of those bodies, we know that fibrine and al- 
bumen so closely resemble each other in constitution that 
they are mutually convertible into each other. During 
the hatching of an egg from its albumen the flesh (fibrine) 
of the young chicken is formed, a phenomenon accom- 
panying the absorption of oxygen from the air. In the 
human system, abundant observation has proved that 
there is a direct connection between the quantity of oxy- 
gen introduced through the lungs and the amount of fibrine 
in the blood. When the respiratory process is unduly 
active the disks oxydize with rapidity, and the amount of 
fibrine increases; but when the reverse takes place, there 
is a restraint on the change of the disks, and the amount 
of fibrine declines. 

The coagulation of the blood is a phenomenon which 
has excited much attention, physiologists generally look- 
ing upon it either as wholly inexplicable, or what, in re- 
ality, amounts to the same thing, as due to the death of 
the blood. What connection there is between its life and 
fluidity, is not so very apparent. A little reflection will, I 
am persuaded, deprive this phenomenon of much of its 
fictitious importance, since it is plain that the coagulation 
of the blood, or, in other words, the separation of fibrine 
from it takes place in the body as well as out of it, for from 
this coagulated fibrine the muscular tissues are formed, 
and from it their waste is repaired. By passing through 
two capillary circulations, the systemic and the pulmona- 
ry, the rapidity of the process is very much interfered 
with; but still, it eventually takes place. 

I here insert one of Lecanu’s analyses of the blood ; it 
may serve to give an idea of the constitution of that liquid. 
It must not be forgotten, however, that such analyses, be- 
yond mere general results, are of little value; the compo- 


What reasons are there for supposing that fibrine may be made in the 
system from albumen or caseine? Does the coagulation of the blood take 
place during life? Of what are the muscular tissues composed? 


PROCESSES OF SECRETION. 


399 


sition of the blood varies incessantly in the same individ- 


ual. 


For instance, the mere accident of his being thirsty, 


or having recently drank abundantly of water, will make 
an entire change in the analysis of the blood. 


WIACCL SD cated Mle Red? cat ot oe ret oh 7 OU L405 
WibrineAget GA ower ew tye ist 271003 
Coloring matter . pee - 133-000. 
Albumen . . MS RR le 65:090. 
Crystalline fatty matter . me: Sane asd. 
Oily matter . a hive 1°310. 
Extractive matter : 1°790. 
Salts and loss 14°135. 

1000-000. 


The following represents the 
sine : 


constitution of hamato- 


Garbor $f FF2 eee .7e.F “ 66°49. 
Heydrocen ist. folie - 5°30. 
Nitrogen ¢ im ° ° 10°50. 
Oxygen : wide La Oos 
Iron . 6°66. 

100°00. 


LECTURE LXXXIX. 


NaturE OF THE Processes or SecretTion.—Origin of 
Secretions.— Phenomena of Respiration.— Arterializa- 
tion — Production of Animal FHeat—Removal of effete 
Matters.— Constitution of Milk.— Uses of that Secretion. 
—Mucus.— Pus.— Bile.— Urine.— Calculi— Bones.— 
Nervous Matter. 


Durine the starvation of an animal all its various se- 
cretions are still formed: a consideration which proves 
that the production of urine, bile, and other such bodies 
is, in reality, connected with the destructive processes 
going on in the animal system. ‘These processes of de- 
cay originate in the action of oxygen admitted by the 
process of respiration. 

The lungs, which constitute the organ by which air is 
introduced, are originally developed as diverticula from 
the oesophagus, and finally become an immense congeries 
of cells emptying into the trachea. In respiration they 
are perfectly passive, the air being introduced and ex- 

What circumstances tend tochange the constitution of the blood? How 


is it known that the secretions arise from destructive processes? What 
is the structure of the lungs ? 


396 ARTERIALIZATION OF BLOOD. 


pelled alternately by muscular contraction. It is com- 
monly estimated that, on an average, about 17 inspira- 
tions are made each minute, and at each inspiration about 
17 cubic inches of air are introduced. 

The blood presents itself on the air cells of a deep blue 
color, and is then known as venous blood. Through the 
thin wall of the cell it obtains oxygen from the air, and 
gives out carbonic acid. It is the coloring matter of 
the disks which discharges this function, and during the 
act of change its tint alters to a bright crimson. It is 
said now to be arterialized, or to constitute arterial blood. 
The magnitude of the scale on which this operation is 
carried forward may be appreciated from the circum- 
stance that in a man of average size, in a single day, about 
seven tons of blood have been exposed to 226 cubic feet 
of atmospheric air. 

The oxygen thus introduced acts directly either on 
the tissues themselves, as it is distributed by the systemic 
circulation, or on the elements of respiration they con- 
tain. In the latter case, carbonic acid gas and water are 
the result; in the former, carbonic acid, water, and am- 
monia. But these changes can not take place without an 
elevation of temperature. Carbon and hydrogen can nei- 
ther burn in the air nor in the animal system without 
evolving heat. The high temperature which an animal 
can maintain is, therefore, directly proportional to the 
quantity of oxygen it consumes. 

The tissues being thus acted upon, give rise, during 
their metamorphoses, to new products, which require to be 
removed from the system ; these, passing under the name 
of secretions, are discharged by glands or other special 
organs. Thus, the carbonic acid, for the most part, es- 
capes from the lungs; the ammonia through the kidneys; 
the water through both those organs and the skin. Lie- 
big has attempted to show that if the elements of urine 
be added to the elements of bile, they will represent the 
elements in the blood; and there can be no doubt that 


How many inspirations does a man make, on an average, in a minute? 
How many cubic inches of air are introduced at each inspiration? What 
is meant by the arterialization of the blood? What action does the oxy- 
gen introduced exert? In what does animal heat arise? Through what 
channels are the leading secretions, water, ammonia, and carbonic acid, 
discharged? What supposed relation is there between the constituents 
of the urine and bile conjointly and those of the blood? 


NUTRITION OF MILK. 397 


the sulphates and phosphates found in the urine arise di- 
rectly from the sulphur and phosphorus previously exist- 
ing in the muscular fibre. 

As an illustration of the principles here given in rela- 
tion to the functions of nutrition and secretion, the con- 
stitution and properties of milk may be cited. The fol- 
lowing is an analysis of it : 


IWViGt Gin: iciifed ste ois ta = leh ioa et Gh 
ULLEE gue ee Sts Mee”. % ae oe ee OU Vos 
Cageine’ jie dspisy ites Gs Cie ae 20) 
Milk sugar. . omar Resid nie, eek dies aes 
Phosphate of lime eal a ase 
$ magnesia “Gh bat dae | *42.. 

"4 $4 TROT) \ (icy Wired? Tgmeionls We aOive 
Chloride of potassium. . . .... 1°44. 
ye © Bodiam: 2". "s cate os 24. 
Soda in combination with caseine . . *42, 
1000°00. 


Of the substances here mentioned, all are undoubtedly 
obtained directly from the food. In the herbage on 
which a graminivorous, milk-giving animal feeds, every 
one of these constituents occurs. I have already shown 
that the butter, or fat, and the caseine are thus directly de- 
rived, and the evidence is equally complete that all the 
salts of phosphoric acid and chlorine arise from the same 
source. 

A young animal, which, in the first periods of its life, is 
nourished exclusively on milk, finds in that milk all the 
various compounds it requires for its own existence and. 
growth. The respiratory food is there—it is the butter 
and milk sugar; the nitrogenized food is there—it is the 
caseine; and we have already seen that albumen and 
caseine are both convertible into fibrine ; the caseine, thus, 
in the mother’s milk, becomes converted into flesh in the 
young animal. ‘To insure the growth of its bones, phos- 
phate of lime (bone earth) is present; there is also chlo- 
rine to form the hydrochloric acid of its gastric juice, and 
soda, which is an essential ingredient in its bile. 

It remains now to add a brief description of the prop- 


erties of the remaining leading animal substances, among 
which may be mentioned: 


From what do the sulphates and phosphates of the urine arise? What 
are the chief constituents of milk? From what source are they derived ? 
What becomes of the butter, milk sugar, caseine, phosphate of lime, chlo- 
rine, and soda in the body of the young animal ? 


L 


398 CHYLE.—BILE.——URINE. 


Cuy.e is usually of a white or reddish white tint. It 
resembles blood in constitution and power of coagulat- 
ing. It contains much fat, which gives to it a cream-like 
aspect. 

Mucus exudes from the surface of mucous membranes. 
It is of a white or yellow color, of a viscid constitution, 
and insoluble in water. It dissolves in a solution of pot- 
ash, and is precipitated by an alkali. 

Pus, a secretion from injured surfaces, resembling mu- 
cus in many respects, but distinguished by not being sol- 
uble in potash solution, but converted by it into a gelat- 
inous body, which can be pulled out in threads. 

Bite, a yellow liquid, secreted by the liver from the 
portal blood; it turns green in the air, has a bitter taste 
and an alkaline reaction, due to the presence ofsoda. Its 
coloring matter is chlorophyl. It is regarded as a 
choleate of soda, the constitution of choleic acid being 
C.,.H;IN;O2. Of the correctness of this formula there is 
considerable doubt, since it has been recently affirmed 
that Taurine, which is a derivative body, contains a large 
amount of sulphur. 

Urine, a yellow-colored fluid, secreted by the kid- 
neys; hasan acid reaction ; its specific gravity from 1:005 
to 1:030; putrefies at a moderate temperature, its urea 
passing into the condition of carbonate of ammonia. The 
chief constituents of urine are urea, uric acid, the sul- 
phates and phosphates of potash, soda, lime, ammonia, 
and a yellow coloring matter, with mucus of the bladder. 

The constitution of the urine changes in disease. In 
Diabetes it contains grape sugar, as may be shown by the 
test of sulphate of copper, already mentioned. Diabetic 
urine may even be fermented with yeast, and alcohol dis- 
tilled from it. , 

Urinary CALcuui are stony concretions often formed 
in the bladder of man and many animals; they are of dif- 
ferent kinds: 1st. Uric acid. 2d. Urate of ammonia. 3d. 
Phosphate of lime, magnesia, and ammonia. 4th. Ox- 
alate of lime, or mulberry calculus. 5th. Cystic and xan- 
thic oxides. 


Whatischyle? What is mucus? How may pus be distinguished from 
mucus? What are the chief properties of bile? From what is it formed ? 
What does taurine contain? What are the chief constituents of urine ? 
How may sugar be detected in diabetic urine? What varieties of uri- 
nary calculi are there ? 


NERVOUS MATTER. 399 


Bones consist of two parts: an animal and an earthy 
matter. The latter is the phosphate of lime (bone earth). 

Nervous Marrer consists of an albuminous substance 
with several fatty principles, distinguished by the remark- 
able fact that they contain phosphorus. In addition, it 
contains chlolesterine. 

It would not agree with the object of these Lectures 
were I here to offer any detailed remarks on the func- 
tions of*the brain and the nervous system. Of the action 
of the lungs, the liver, the kidneys, or other such organs, 
we are beginning to have a very distinct idea; but it is 
altogether different with the functions of the cerebro-spi- 
nal axis; there every thing is in mystery and darkness ; 
yet it is in what may be hereafter discovered in relation 
to the action of this system that our chief hopes of the ad- 
vance of animal chemistry and physiology depend. 


Of what are bones composed? What are the chief constituents of 
nervous matter? 


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INDEX. 


As Acid, glucic, 316. 
Absolute alcohol, 323. hippuric, 346. 
Acetal, 332. hydriodic, 236. 
Acetification, 332. hydrochloric, 231. 
Acetone, 335. hydrocyanic, 351. 
Acetyle compounds, 331. hydroferrocyanic, 355. 
Acid, acetic, 332. hydrofluoric, 238. 


aconitic, or equisetic, 364. 
aldehydic, 331. 
alloxanic, 360. 
amygdalinic, 353. 
anilic, or indigotic, 374. 
anthranilic, 374. 
antimonic, 293. 
antimonious, 293. 
apocrenic, 384. 
arsenic, 292. 
arsenious, 288. 
tests for, 289. 
benzoic, 344. 
boracic, 246. 
butyric, 321. 
capric and caproic, 378. 
carbolic, 382. 
carbonic, 241. 

liquefaction of, 243. 
chloracetic, 334. 
chloric, 230. 
chlorous, 230. 
chloro-valerisic, 343. 
chromic, 286. 
chrysammic, 374. 
chrysanilic, 374. 
cinnamic, 349, 
citric, 364. 
comenic, 369. 
crenic, 383. 
croconic, 318. 
cyanic, 353. 
cyanuric, 354. 
dialuric, 361. 
elaidic, 378. 
ellagic, 366. 
ethalic, 378. 
ethionic, 330. 
ferric, 279. 
formic, 340. 
fulminic, 354. 
faumaric, 365. 
gallic, 366. 


hydrofluosilicic, 248. 
hydrosalicylic, 347. 
hydrosulphocyanic, 357. 
hydrosulphuric, 220. 
hyperchloric, 230. 
hyperchlorous, 230. 
hypermanganic, 275. 
hyponitrous, 207. 
hyposulphuric, 219. 
hyposulpharous, 219. 
igasuric, 370. 
isatinic, 374. 
isethionic, 330. 
japonic, 365. 

kinic, 370. 

lactic, 324. 

lithic, 359. 

maleic, 365. 

malic, 364. 
manganic, 274. 
margaric, 377. 
meconic, 369. 
melanic, 348. 
melasinic, 316. 
mesoxalic, 360. 
metagallic, 366. 
metaphosphoric, 225. 
mucic, 318. 
muriatic, 231. 
mykomelinic, 360. 
myristic, 378. 

nitric, 209. 
nitromuriatic, 234. 
nitrous, 208. 
cenanthic, 327. 

oleic, 377. 

oxalic, 316. 
oxalhydric, 318. 
oxaluric, 360. 
palmitic, 378. 
parabanic, 360. 
pectic, 314. 
phosphoric, 224. 


Lu? 


402 


Acid, phosphorous, 224. 
phosphovinic, 328. 
picric, or carbazotic, 374. 
pinic, sylvic and pimaric, 380. 
purpuric, 361. 
pyrogallic, 366. 
pyroligneous, 332. 
pyromeconic, 369. 
pyrophosphoric, 225. 
pyrotartaric, 363. 
racemic, 363. 
rhodizonic, 318. 
rubinic, 365. 
saccharic, 318. 
sacchulmic, 316. 
salicylic, 347. 
sebacic, 378. 
silicic, 247. 
stearic, 377. 
suberic, 378. 
succinic, 378. 
sulphamilic, 343. 
sulphindigotic, 373. 
sulphobenzoic, 344. 
sulphoglyceric, 377. 
sulphomethylic, 340. 
sulphonaphthalic, 382. 
sulphosaccharic, 315. 
sulphovinic, 327. 
sulphuric, 217. 
sulphurous, 215. 
tannic, 365. 
tartaric, 362. 
thionuric, 360. 
ulmic, 316, 383. 
uramilic, 361. 
uric, 359. 
valerianic, 343. 
xanthic, 336. 

Acids, coupled, 362. 

Aconitine, 370. 

Affinity, chemical, 164. 

Albumen, 389-390. 

vegetable, 389. 

Alcargen, 338. 

Alcohol, 323. 

Aldehyde, 331. 

Alizarine, 372. 

“ Alkarsin, 337. 

Allantoin, 359. 

Alloxan, 359. 

Alloxantine, 361. 

Alumina, 271. 

sulphates, 273. 

Aluminum, 271. 

Alums, 273. 

Amalgamation process, 299. 

Amalgams, 303. 

Amidine, 312. 

Amidogen, 249. 


INDEX. 


Amilen, 343. 
Ammeline and ammelide, 357. 
Ammonia, carbonate, 350. 
nitrate, 350. 
preparation and proper- 
ties of, 249, 349. 
sulphate, 350. 
Ammoniacal amalgam, 250, 349. 
Ammonium, 250. 
chloride, 350. 
sulphurets, 251. 
Amyegdaline, 352. 
Amyle compounds, 342. 
Anatto, 372. 
Aniline, 367, 371, 373. 
Animal chemistry, 384. 
Anthracite, 239. 
Antiarine, 370. 
Antimony, 292. 
chloride, 293. 
oxide, 293. 
sulphurets, 294. 
Aqua regia, 234. 
Arabine, 314. 
Argol, 322. 
Aricine, 370. 
Arrow-root, 312. 
Arsenic, 287. 
sulphurets, 292. 
Arterialization, 396. 
Arterial membrane, 391. 
Atmosphere, composition of, 191. 
physical constitution 
of, 190. 
Atmospheric pressure, 192. 
Atomic weights, 145. 
Atoms, 5. 
Atropine, 370. 
Aurum musiyum, 285. 
Azote, 188. 


Balloons, 16. 
Balsams, 381. 


Barium, 264. 


chloride, 265. 

oxides, 265. 

sulphuret, 265. 
Barley sugar, 313. 
Barometer, 200. 
Baryta, 265. 

carbonate, 266, 

sulphate, 266. 
Bassorine, 314. 
Batteries, voltaic, 120. 
Bell metal, 296. 
Benzamide, 345. 
Benzine, 346. 
Benzoine, 345. 
Benzone, 346. 


INDEX. 


Benzyle compounds, 344. 
Bile, 398. 
Biscuit-ware, 272. 
Bismuth, 299. 
nitrates, 299. 
oxides, 299. 
Bleaching powder, 269. 
Blood, composition of, 395. 
Boiling points of fluids, 47. 
Bone earth, 269. - 
Bones, composition of, 399. 
Boron, 246. . 
Brain, composition of, 399. 
Brass, 296. 
British gum, 313. 
Bromine, preparation and properties 
of, 237. ; 
Brucia, 370. 
Buify coat, 391. 
Butyrine, 378. 


C. 


Cadmium, 283. 
compounds of, 283. 
Caffeine, 370. 
Calamine, electric, 283. 
Calcium, 267. 
chloride, 268. 
fluoride, 268. 
sulphurets of, 268. 
Calculi, urinary, 398. 
Calomel, 302. 
Calorimeter, 29. 
Camphor, 379. 
artificial, 379. 
Caoutchouc, 380. 
Capacity for heat, 28. 
Caramel, 313. 
Carbon, 238. 
chlorides of, 329. 
its compounds with oxygen, 
240. 
sulphuret of, 246. 
Carbonic oxide, preparation and 
properties of, 240. 
Carbyle, sulphate of, 330. 
Carmine, 374. 
Carthamine, 372. 
Caseine, 389-390. 
vegetable, 389. 
Cassava, 312. 
Cast iron, 277. 
Catechin and catechu, 365. 
Cedriret, 382. 
Cellulose, 315. 
Cerine, 378. 
Cerium, 273. 
Chameleon, mineral, 275. 
Charcoal, properties of, 239. 
Chinoidine, 370. 


403 


Chloral, 335. 
Chloric acid, 230. 
Chlorine, 226. 
compounds with oxygen, 
229. 
preparation and properties 
of, 227. 
Chlorisatine, 374. 
Chlorocinnose, 349. 
Chloroform, 341. 
Chlorophyle, 372. 
Chlorosamide, 348. 
Chlorureted acetic ether, 336. 
formic ether, 336. 
Chlorous acid, 230. 
Cholesterine, 378. 
Chondrine, 391. 
Chrome yellow, 287. 
Chromic acid, salts of, 287. 
oxide, salts of, 286. 
Chromium, 285. 
oxide, 285. 
Chyle, 386, 398. 
Chyme, 386. 
Cinchona, 369. 
Cinnabar, 303. 
Cinnamyle compounds, 348. 
Circulation of blood, 392. 
Clays, composition of, 271. 
Clay iron stone, 276. 
Coagulation, 394. 
Coal, 384. 
oil, 382. 
Cobalt, 281. 
characters of salts of, 281. 
chloride, 282. 
oxalate, 281. 
oxides, 281. 
Cobaltocyanogen, 357. 
Cocoa tallow, 378. 
Codeine, 368. 
Cohesion, 7. 
Colchicine, 370. 
Cold rays, 69. 
Colophony, 380. 
Coloring principles, 371. 
Colors, 82. 
Columbium, 287. 
Combination, by volumes, 154. 
laws of, 151. 
Combining numbers, 153. 
table of, 145. 
Combustion, 174. 
Compound radicals, 309. 
Condensation of vapors, 45. 
Conicine, or conia, 370. 
Copper, 295. 
alloys of, 296. 
arsenite, 296. 
carbonates, 296. 


404 


Copper, nitrate, 296. 
oxides, 295. 
sulphate, 296. 

Corrosive sublimate, 303. 

Creasote, 381. 

Cryophorus, 50. 

Crystallization ; crystallography, 

156. 

Cupellation, 300. 

Curarine, 370. 

Cyamelide, 353. 

Cyanides, metallic, 353. 

Cyanogen, 245, 350. 

chlorides of, 355. 

Cystic oxide, 361. 


D. 


Daguerreotype, 92. 
Dammar resin, 380. 
Daphnine, 370. 

Daturine, 370. 
Decomposition of water, 124. 
Delphinine, 370. 

Deutoxide of nitrogen, 206. 
Dew, 69. 

Dew-point, 52. 

Dextrine, 312. 

Diamond, 239. 

Diastase, 312. 

Differential thermometer, 17. 
Diffusion of gases, 202. 
Digestion, 386. 

Dimorphism, 160. 
Dispersion, 74. 

Dragon’s blood, 380. 

Dross, 297. 

Dutch liquid, 329. 


E. 


Earthen-ware, manufacture of, 272. 

Ebullition, 44. 

Elaidine, 378. 

Elaldehyde, 331. 

Elaterine, 370. 

Electricity, action of, on the magnet, 

133. 

animal, 142. 
conduction of, 99. 
of steam, 142. 
statical, 97. 
voltaic, 115. 

Electro-chemistry, 125. 

Electrolysis, 126. 

Electrometers, 112. 

Electrotype, 129. 

Electrophorus, 115. 

Emetine, 370. 

Emulsine, 352. 

Enamel, 284. 

Equivalent numbers, 145. 


INDEX. 


Equivalent numbers, table of, 145. 
Eremacausis, 310. 
Essences, 379. 
Ethal, 378. 
Ether, 324. 
continuous process for, 328. 
Ethers, compound, 326. 
Ether, heavy muriatic, 335. 
Etherole and etherine, 330. 
Ethyle group, 325. 
Eudiometer, Ure’s, 190. 
Eupione, 381. 
Evaporation, 55. 
at low temperatures, 
56. 
Expansion of solids, 23. 
fluids, 18. 
gases, 19. 


F 


Faraday’s theory of polarization, 113. 
Fatty bodies, 375. 
Fermentation, alcoholic, 320. 
lactic, 321, 324. 

Ferridcyanogen compounds, 356. 
Ferrocyanogen compounds, 355. 
Fibrine, 389. 

vegetable, 389. 
Fixed air, 242. 
Flame, structure of, 176. 
Fluoride of boron, 247. 
Fluorine, 237. 
Formomethylal, 341. 
Freezing of water by evaporation, 

dl. 

Freezing mixtures, 37. 
Fusel oil, 342. 
Fusible metal, 299. 


G. 


Galvanism, 116. 
Galvanometer, 135. 
Gamboge, 372. 
Gay-Lussac’s law, 204. 
Gelatine, 391. 
Gentianine, 370. 
Geoffroy’s tables, 167. 
Glass, manufacture of, 272. 
soluble, 273. 
Globuline, 393. 
Glucinum, 273. 
Glucose, 313. 
Glycerine, 376, 377. 
Gold, 303. 
compounds of, 304. 

Goniometers, 159. 
Goulard’s water, 334. 
Graphite, 239. 
Gravity, specific, of gases, determi- 

nation of, 155. 


INDEX. 


Green, Scheele’s, 296. 
Grove’s battery, 122. 
Gum, British, 313. 
Arabic, 314. 
tragacanth, 314. 
Gunpowder, 260. 
Gypsum, 269. 
H. 
Hemaphein, 393. 
Hematite, 276. 
Hair, 391. 
Hare’ s batteries, 121-131. 
blow-pipe, 182. 
Heat, animal, 396. 
capacity for, 28. 
conduction of, 56, 
exchanges of, 67. 
latent, 36. 
radiation, reflection, absorp- 
tion, and transmission of, 63. 
varieties of, 67. 
Hematine, 393. 
Hematoxyline, 372. 
Hesperidine, 370. 
Horn, 391. 
Hydrobenzamide, 345. 
Hydrogen, antimoniureted, 294. 
arseniureted, 292. 
light carbureted, 243. 
peroxide of, 188. 
persulphuret of, 222. 
phosphureted, 226. 
preparation and proper- 
ties of, 178. 
sulphureted, 220. 
Hygrometer, Daniell’s, 52. 
Hygrometry, 51. 
Hyoscyamine, 370. 
Hyponitrous acid, 207. 
Hyposulphurous acid, 219. 


I. 


Ideal coloration, 94. 

Idrialine, 384. 

Indigo, 373. 

Induction, 102. 

Interference, 83. 

Interstices, 6. 

Inuline, 312. 

Jodine, preparation and properties 

of, 234. 

Iridium, 306. 

Iron, 276. 
carbonate, 280. 
cast, varieties of, 277. 
characters of salts of, 278. 
chlorides, 280. 
manufacture, 276. 
oxides of, 278. 
passive, 278. 


405 


Iron, sulphates, 280. 
sulphurets, 280. 
Isatine, 374. 
Isomerism, 162. 
Isomorphism, 161. 


K. 


Kakodyle and its compounds, 337. 
Kapnomor, 382. 

Kermes mineral, 294. 

Kyanol, 382. 


L. 
Lac, 380. 
Lactine, 314. 
Lampblack, 239. 
Lamps, safety, 58. 
Lanthanium, 273. 
Latent heat, 36. 
Laughing gas, 205. 
Laws of combination, 151. 
Lead, 297. 
action of water on, 297. 
alloys of, 299. 
carbonate, 298. 
characters of salts of, 298. 
chloride, 298. 
lodide, 298. 
nitrate, 299. 
oxides, 298. 
Leaven, 319. 
Lecanorine, 374. 
Leiocome, 313. 
Leukol, 371. 
Leyden jars, 108. 
Light, cause of, 71. 
chemical action of, 77. 
reflection, refraction, and po- 
larization of, 87-89. 
wave theory, 71, 78. 
Lignine, 315. 
Lignite, 383. 
Lime, 267. 
carbonate, 268. 
chloride, 269. 
phosphate, 269. 
salts, characters of, 268. 
sulphate, 269. 
Liquor of Libayius, 285. 
Lithium, 264. 
Litmus, 374. 


M. 
Madder, 372. 
Magnesia, 269. 
carbonate, 270. 
characters of salts of, 270. 
phosphate, 271. 
sulphate, 270. 
Magnesium, preparation and grap 
erties of, 269. 


406 


Magnetism, 134. 
Magnets, artificial, 137. 
Magneto-electricity, 139. 
Malachite, 296. 
Manganese, characters of salts of, 
274. 
chloride, 275. 
oxides of, 274. 
preparation and prop- 
erties of, 274. 
sulphate, 276. 
Margarine, 376, 377. 
Margarone, 377. 
Marriotte, law of, 43, 203. 
Marsh’s test for arsenic, 290. 
Maximum density, 21. 
Meconine, 368-370. 
Medicated waters, 379. 
Melam and melamine, 357. 
Mellon, 358. 
Mercaptan, 336. 
Mercury, 302. 
characters of salts of, 303. 
chlorides, 302. 
iodides, 303. 
nitrates, 303. 
oxides of, 302. 
sulphates, 303. 
sulphurets, 303. 
Mesityle, 335. 
Metaldehyde, 331. 
Metal, fusible, 299. 
Metals, general properties of, 252. 
classification of, 253. 
Methyle compounds, 338. 
Microcosmic salt, 264. 
Milk, composition of, 397. 
Mindererus spirit, 333. 
Mineral chameleon, 275. 
Molybdenum, 287. 
Mordants, 272. 
Morphia, 368. 
Mosaic gold, 285. 
Mucilage, 314. 
Mucus, 398. 
Multipliers, 135. 
Murexan, 361. 
Murexide, 361. 
Muscovado sugar, 313. 
Myricine, 378. 


N. 


Naphtha, 382-384. 
Naphthaline, 382. 
Narceine, 368. 
Narcotine, 368. 
Nervous substance, 399. 
Nickel, 281. 

sulphate, 281. 
Nihil album, 282. 


INDEX. 


Nitric acid, 209. 
Nitrobenzide, 346. 
Nitrogen, chloride of, 231. 
its compounds with oxy- 
gen, 189. 
preparations and proper- 
ties of, 188. 
Nitrous acid, 208. . 
oxide, 205. 
Nomenclature, 144. 
Nutmeg butter, 378. 
Nutrition, function of, 392. 


O. 


Qinanthic ether, 327. 

Ohm’s theory, 131. 

Oils and fats, 375. 

Oil of bitter almonds, 344. 
cajeput, 379. 
cinnamon, 348. 
copaiba, 379. 
horseradish, 379. 
lavender, 379. 
lemons, 379. 
mustard, 379. 
peppermint, 379. 
rosemary, 379. 
spirea, 347. 
storax, 379. 
turpentine, 379. 
vitriol, preparation of, 217 
wine, heavy, 329. 

Oils, palm and cocoa, 378. 

volatile, 378. 

Oleine, 376, 377. 

Olefiant gas, 244. 

Orcine, orceine, 374. 


| Organic bodies, classification of, 311. 


decomposition of, by 
heat, 308. 
general characters 
iy SUN 
chemistry, 307. 
Orpiment, 292. 
Osmium, 287. 
Oxalates, 317. 
Oxamethane, 327. 
Oxamide, 318, 326. 
Oxygen, preparation and properties 
of, 169. 
Ozokerite, 384. 


P. 


Palladium, 304. 
Palmitine, 378. 

Palm oil, 378. 
Papin’s digester, 45. 
Paracyanogen, 351. 
Parafiine, 381. 
Paranaphthaline, 382. 


INDEX. 


Paschal’s experiment, 201. 
Pectine, 314. 
Perchloric acid, 230. 
Petroleum, 384. 
Pewter, 285. 
Phloridzine, 370. 
Phosphorescence, 78, 96. 
Phosphoric acid, 224. 
Phosphorus, compounds with oxy- 
gen, 223. 
preparation and proper- 
ties of, 222. 
Phosphureted hydrogen, 226. 
Photography, 93. 
Picamar, 382. 
Picrotoxine, 370. 
Pile, voltaic, 120. 
Piperine, 370. 
Pitch, 381. 
Pit-coal, 384. 
Pittakal, 382. 
Plasma, 393. 
Platinum, 304. 
black, 305. 
chlorides, 305. 
oxides, 305. 
power of determining un- 
ion of gases, 305. 
salts, combustible, 371. 
spongy, 305. 
Plumbago, or graphite, 239. 
Polarization of light, 87. 
Populine, 370. 
Porcelain, manufacture of, 272. 
Potassium, chloride of, 259. 
iodide of, 259. 
peroxide of, 257. 
preparation and proper- 
ties of, 256. 
sulphurets of, 259. 
Potash, 257. 
bicarbonate, 259. 
bisulphate, 259. 
carbonate, 259. 
chlorate, 260. 
hydrate of, 257. 
nitrate, 260. 
salts, test for, 258. 
sulphate, 259. 
Potato oil and its compounds, 342. 
Prism, 74. 
Proteine, 391. 
Prussian blue, 356. 
Pseudomorphine, 368. 
Purple of Cassius, 284-304. 
Pus, 398. 
Putty powder, 284. 
Pyroacetic spirit, 335. 
Pyrometer, 23. 
Daniell’s, 27. 


407 


Pyroxylic spirit, 339. 
Q. 
Quercitron bark, 372. 
Quicksilver, 302. 
Quina, 369. 
Quinoline, 371. 


R. 


Radiation, 63. 

Rays of the sun, chemical, 91. 
Realgar, 292. 

Reflection, law of, 89. 
Refraction, law of, 74, 89. 
Resins, 380. 

Respiration, 176. 

Rhodium, 306. 


8. 
Sacchulmine, 316. 
Safety jet, Hemming’s, 58. 
Safety lamp, 58. 
Sago, 312. 
Salicine, 347, 370. 
Salicyle compounds, 347. 
Scheele’s green, 296. 
Secretion, 395. 
Selenium, 222. 
Silicon, 247. 
Silver, 299. 
ammoniuret, 301. 
characters of salts of, 300. 
chloride, 301. 
German, 281. 
iodide, 301. 
nitrate, 301. 
oxides, 300. 
sulphuret, 301. 
Smalt, 281. 
Soaps ; saponification, 376. 
Soda, biborate, 264. 
bicarbonate, 263. 
carbonate, 262. 
hydrate of, 261. 
nitrate, 263. 
phosphates of, 263. 
sulphate, 263. 
Soda water, 242. 
Sodium, chloride, 261. 
preparation and properties 
of, 260. 
Solanine, 370. 
Solder, 285. 
Specific gravity, 155. 
heat, 28. 
Spectres, 96. 
Spectrum, solar, 75-78 
Speculum metal, 296. 
Spermaceti, 378. 
Spirea ulmaria, oil of, 347. 
Starch, 310. 


408 


Steam, elastic force of, 49. 
engine, 46, 55. 
Stearine, 376. 
Stearopten, 379. 
Steel, 277. 
Stone-ware, manufacture of, 272. 
Strontia, 266. 
nitrate, 267. 
sulphate, 267. 
Strontium, 266. 
chloride, 267. 
Strychnia, 370. 
Sublimate, corrosive, 303. 
Substitution, 310. 
Sugar, cane, 313. 
eucalyptus, 314. 
from ergot of rye, 314. 
grape, 313. 
of diabetes insipidus, 313. 
of milk, 314. 
Sulphobenzide, 346. 
Sulphocyanogen compounds, 357. 
Sulphur compounds with oxygen, 
215. 
occurrence in nature, 212. 
properties of, 214. 
Sulphureted hydrogen, 220. 
Sulphuric acid, 217. 
Sulphurous acid, 215. 
Symbols, 147. 
table of, 145. 
Synaptase, 352. 
Systems, crystallographical, 156. 


sia 


Tapioca, 312. 
Tar, varieties of, 381. 
Tartar, cream of, 363. 
Taurine, 398. 
Tellurium, 294. 
Thebaine, 368. 
Theine, 370. 
Theobromine, 370. 
Thermoelectricity, 139. 
Thermometer, Breguet’s, 36. 
construction of, 19. 
differential, 17. 
Sanctorio’s, 17. 
scales, 20. 
Thorium, 273. 
Tin, 283. 
chlorides, 284. 
oxides, 284. 
sulphurets, 285. 
Tinned plate, 285. 
Titanium, 287. 
Tithonic rays, 91. 
Transverse vibrations, 81. 
Tungsten, 287. 


INDEX. 


Turmeric, 372. 
Turpeth mineral, 303. 
Type metal, 294. 
Types, chemical, 310. 


U. 


Ulmine, 316, 383. 
Undulatory theory, 78. 
Uramile, 360. 

Uranium, 294. 

Urea, 354, 358. 

Urinary calculi, 398. 
Urine, composition of, 398. 


vs 


Vanadium, 287. 
Vapor, elastic force of, 49. 
Vapors, density of, 53. 
nature of, 39. 
Vaporization at low temperatures, 
laws of, 40. 
Vegeto alkalis, 367. 
Veratria, 370. 
Verdigris, 334. 
Vermilion, 303. 
Vinegar, 332. 
Vitriol, blue, 296. 
green, 280. 
oil of, 218. 
white, 283. 
Voltameter, 130. 
Volumes, combination by, 154. 


WV 


W ater, composition of, 126, 183. 
of crystallization, 187. 
W aves, length of, 86. 
W ax, 378. 
Wines, 322. 
Wire gauze, 58. 
W ood-spirit and its compounds, 338, 
ether, 339. 
Woody fibre, 315. 


X. 


Xanthic acid, 336. 


oxide, 361. 
Xyloidine, 319. 


Y. 


Yeast, 320. 
Yttrium, 273. 


a 
Zaffre, 281. 
Zinc, 282. 
oxide of, 282. 
silicate, 283. 
sulphate, 283. 
Zirconium, 273. 


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